Patient-based parameter generation systems for medical injection procedures

ABSTRACT

A system includes a parameter generation system to determine parameters of at least one phase of an injection procedure based at least in part upon a type of the injection procedure. The parameter generator system determines the amount of a pharmaceutical that is to be delivered to a patient at least in part on the basis of the concentration of an agent in the pharmaceutical and at least on part on the basis of a function that depends upon and varies with a patient parameter. The patient parameter can, for example, be weight, body mass index, body surface area or cardiac output. The pharmaceutical can, for example, include a contrast enhancing agent for use in an imaging procedure.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit of PCT Application US07/026194, filedDec. 21, 2007 and U.S. Provisional Application Ser. No. 60/877,779,filed on Dec. 29, 2006, and U.S. Provisional Patent Application Ser. No.60/976,002, filed Sep. 28, 2007, the contents of which are herebyincorporated by reference.

RELATED APPLICATIONS

This application contains subject matter that may be related to thatdisclosed and/or claimed in Published PCT Application No. WO/2006/058280(PCT International Patent Application No. PCT/US05/042891), filed onNov. 23, 2005 and Published PCT Application No. WO/2006/055813 (PCTInternational Patent Application No. PCT/US2005/041913), filed on Nov.16, 2005, the disclosures of which are incorporated herein by referenceand made a part hereof.

BACKGROUND OF THE INVENTION

The present invention is related to devices, systems and methods forfluid delivery, and, particularly, to devices, systems and methods fordelivery of a pharmaceutical fluid to a patient, and, especially fordelivery of a contrast medium to a patient during a medical injectionprocedure.

The following information is provided to assist the reader to understandthe invention disclosed below and the environment in which it willtypically be used. The terms used herein are not intended to be limitedto any particular narrow interpretation unless clearly stated otherwisein this document. References set forth herein may facilitateunderstanding of the present invention or the background of the presentinvention. The disclosures of all references cited herein areincorporated by reference.

The administration of contrast medium (with, for example, a poweredinjector) for radiological exams typically starts with the clinicianfilling an empty, disposable syringe with a certain volume of contrastagent pharmaceutical. In other procedures, a syringe pre-filled withcontrast agent is used. The clinician then determines a volumetricflow-rate and a volume of contrast to be administered to the patient toenable a diagnostic image. An injection of saline solution, having avolume and flow rate determined by the operator, often follows theadministration of contrast agent into the veins or arteries. A number ofcurrently available injectors allow for the operator to program aplurality of discrete phases of volumetric flow rates and volumes todeliver. For example, the SPECTRIS SOLARIS® and STELLANT® injectorsavailable from Medrad, Inc. of Indianola, Pa., provide for entry of upto and including six discrete pairs or phases of volumetric flow rateand volume for delivery to a patient (for example, for contrast and/orsaline). Such injectors and injector control protocols for use therewithare disclosed, for example, in U.S. Pat. No. 6,643,537 and PublishedU.S. Patent Application Publication No. 2004-0064041, assigned to theassignee of the present invention, the disclosures of which areincorporated herein by reference. The values or parameters within thefields for such phases are generally entered manually by the operatorfor each type of procedure and for each patient undergoing aninjection/imaging procedure. Alternatively, earlier manually enteredvalues of volume and flow rate can be stored and later recalled from thecomputer memory. However, the manner in which such parameters are to bedetermined for a specific procedure for a specific patient are not welldeveloped.

In that regard, differences in contrast dosing requirements fordifferent patients during imaging and other procedures have beenrecognized. For example, U.S. Pat. No. 5,840,026, assigned to theassignee of the present invention, the disclosure of which isincorporated herein by reference, discloses devices and methods tocustomize the injection to the patient using patient specific dataderived before or during an injection. Although differences in dosingrequirements for medical imaging procedures based upon patientdifferences have been recognized, conventional medical imagingprocedures continue to use pre-set doses or standard delivery protocolsfor injecting contrast media during medical imaging procedures. Giventhe increased scan speed of recently available CT scanners includingMDCT (or MSCT) scanners, single phase injections are dominant overbiphasic or other multiphasic injections in regions of the world wheresuch fast scanners are used. Although using standard, fixed orpredetermined protocols (whether uniphasic, biphasic or multiphasic) fordelivery simplifies the procedure, providing the same amount of contrastmedia to different patients under the same protocol can produce verydifferent results in image contrast and quality. Furthermore, with theintroduction of the newest MDCT scanners, an open question in clinicalpractice and in the CT literature is whether the standard contrastprotocols used with single-slice, helical scanners will translate wellto procedures using the MDCT machines. See, for example, Cademartiri, F.and Luccichenti, G., et al., “Sixteen-row multislice computedtomography: basic concepts, protocols, and enhanced clinicalapplications.” Semin Ultrasound CT MR 25(1): 2-16 (2004).

A few studies have attempted quantitative analyses of the injectionprocess during CT angiography (CTA) to improve and predict arterialenhancement. For example, Bae and coworkers developed pharmacokinetic(PK) models of the contrast behavior and solved the coupled differentialequation system with the aim of finding a driving function that causesthe most uniform arterial enhancement. K. T. Bae, J. P. Heiken, and J.A. Brink, “Aortic and hepatic contrast medium enhancement at CT. Part I.Prediction with a computer model,” Radiology, vol. 207, pp. 647-55(1998); K. T. Bae, “Peak contrast enhancement in CT and MR angiography:when does it occur and why? Pharmacokinetic study in a porcine model,”Radiology, vol. 227, pp. 809-16 (2003); K. T. Bae et al., “MultiphasicInjection. Method for Uniform Prolonged Vascular Enhancement at CTAngiography: Pharmacokinetic Analysis and Experimental Porcine Method,”Radiology, vol. 216, pp. 872-880 (2000); U.S. Pat. Nos. 5,583,902,5,687,208, 6,055,985, 6,470,889 and 6,635,030, the disclosures of whichare incorporated herein by reference. An inverse solution to a set ofdifferential equations of a simplified compartmental model set forth byBae et al. indicates that an exponentially decreasing flow rate ofcontrast medium may result in optimal/constant enhancement in a CTimaging procedure. However, the injection profiles computed by inversesolution of the PK model are profiles not readily realizable by most CTpower injectors without major modification.

In another approach, Fleischmann and coworkers treated thecardiovascular physiology and contrast kinetics as a “black box” anddetermined its impulse response by forcing the system with a short bolusof contrast (approximating an unit impulse). In that method, oneperforms a Fourier transform on the impulse response and manipulatesthis transfer function estimate to determine an estimate of a moreoptimal injection trajectory than practiced previously. D. Fleischmannand K. Hittmair, “Mathematical analysis of arterial enhancement andoptimization of bolus geometry for CT angiography using the discreteFourier transform,” J Comput Assist Tomogr, vol. 23, pp. 474-84 (1999),the disclosure of which is incorporated herein by reference.

Uniphasic administration of contrast agent (typically, 100 to 150 mL ofcontrast at one flow rate) results in a non-uniform enhancement curve.See, for example, D. Fleischmann and K. Hittmair, supra; and K. T. Bae,“Peak contrast enhancement in CT and MR angiography: when does it occurand why? Pharmacokinetic study in a porcine model,” Radiology, vol. 227,pp. 809-16 (2003), the disclosures of which are incorporated herein byreference. Fleischmann and Hitmmair thus presented a scheme thatattempted to adapt the administration of contrast agent into a biphasicinjection tailored to the individual patient with the intent ofoptimizing imaging of the aorta. A fundamental difficulty withcontrolling the presentation of CT contrast agent is that hyperosmolardrug diffuses quickly from the central blood compartment. Additionally,the contrast is mixed with and diluted by blood that does not containcontrast.

Fleischmann proscribed that a small bolus injection, a test bolusinjection, of contrast agent (16 ml of contrast at 4 ml/s) be injectedprior to the diagnostic scan. A dynamic enhancement scan was made acrossa vessel of interest. The resulting processed scan data (test scan) wasinterpreted as the impulse response of the patient/contrast mediumsystem. Fleischmann derived the Fourier transform of the patienttransfer function by dividing the Fourier transform of the test scan bythe Fourier transform of the test injection. Assuming the system was alinear time invariant (LTI) system and that the desired output timedomain signal was known (a flat diagnostic scan at a predefinedenhancement level) Fleischmann derived an input time signal by dividingthe frequency domain representations of the desired output by that ofthe patient transfer function. Because the method of Fleischmann et. al.computes input signals that are not realizable in reality as a result ofinjection system limitations (for example, flow rate limitations), onemust truncate and approximate the computed continuous time signal.

In addition to control of a powered injector to provide a desired timeenhancement curve, the operation of a powered injector should becarefully controlled to ensure the safety of the patient. For example,it is desirable not to exceed a certain fluid pressure during aninjection procedure. In addition to potential hazards to the patient(for example, vessel damage) and potential degradation of the diagnosticand/or therapeutic utility of the injection fluid, excessive pressurecan lead to equipment failure. Disposable syringes and other fluid pathcomponents (sometimes referred to collectively as a “disposable set”)are typically fabricated from plastics of various burst strengths. Ifthe injector causes pressure in the fluid path to rise above the burststrength of a disposable fluid path element, the fluid path element willfail.

In addition to problems of control with current injector systems, manysuch systems lack convenience and flexibility in the manner in which theinjector systems must be operated. In that regard, the complexity ofmedical injection procedures and the hectic pace in all facets of thehealth care industry place a premium on the time and skills of anoperator.

Although advances have been made in the control of fluid deliverysystems to, for example, provide a desirable time enhancement curve andto provide for patient safety, it remains desirable to develop improveddevices, systems, and method for delivery of fluids to a patient.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides system including aparameter generation system to determine parameters of at least onephase (for example, of the plurality of phases) of an injectionprocedure based at least in part upon a type of the injection procedure.The parameter generator system determines the amount of a pharmaceuticalthat is to be delivered to a patient at least in part on the basis ofthe concentration of an agent in the pharmaceutical and at least on parton the basis of a function that depends upon and varies with a patientparameter. The patient parameter can, for example, be weight, body massindex, body surface area or cardiac output. The pharmaceutical can, forexample, include a contrast enhancing agent for use in an imagingprocedure.

In one embodiment at least a first portion of the volume of thepharmaceutical to be injected is calculated using the formula:V₁=weight*X*Y, wherein V₁ is the first portion of the volume, X is afunction of weight, and Y is a function of the concentration of contrastenhancing agent in the pharmaceutical. X can, for example, be determinedfor a particular patient weight (or other patient parameter) from analgorithm in which X is calculated as a function of weight. X canalternatively be determined for a particular patient weight (or otherpatient parameter) from a table wherein X is set forth as a function ofweight.

V₁ can, for example, be the volume of the pharmaceutical to be deliveredin a phase in which only the pharmaceutical is to be delivered. Theparameter generation system can also determine a volume V₂ ofpharmaceutical to be delivered in at least a second phase in which boththe pharmaceutical and a diluent are to be delivered to the patient. Theflow rate of the pharmaceutical in the first phase can be established tobe approximately equal to the flow rate of admixture of pharmaceuticaland diluent fluid in the second phase.

The flow rate of the pharmaceutical (in the first phase) can, forexample, be calculated by dividing V₁ by an injection duration of thefirst phase. The injection duration of the first phase can, for example,be determined by adding a factor K to a scan duration of an imagingsystem. K can, for example, be in the range of approximately 0 toapproximately 10 seconds. A minimum first phase injection duration canalso be input into the parameter generation system.

The volume V₂ of contrast to be delivered to the patient in the secondphase can, for example, be calculated based at least in part on apatient parameter. The patient parameter can, for example, be weight,body mass index, body surface area or cardiac output. In one embodiment,the volume V₂ is determined by the formula V₂=weight*Z, wherein Z is aconstant.

The volume of saline to be delivered to the patient can, for example, becalculated from V₂ and a ratio of pharmaceutical to diluent fluid in thesecond phase.

The parameter generation system can determine whether the total volumeof the pharmaceutical to be delivered to the patient in all phasesexceeds the volume pharmaceutical available for delivery to the patient(for example, exceeds the volume of a container for the pharmaceuticalfrom which pressurized pharmaceutical will be delivered to the patient).In such an embodiment, the parameter generation system can include rulesto reduce the total volume of the pharmaceutical if the determined totalvolume exceeds the available volume. For example, the total volume canreduced so that the reduced total volume of the pharmaceutical to bedelivered to the patient does not exceed the volume of a container fromwhich the pharmaceutical is to be delivered.

Further, a determination can be made by the parameter generation systemof whether the flow rate of the pharmaceutical during the first phasewill exceed a predetermined flow rate. In such an embodiment, theparameter generation system can include rules to, for example, adjust V₁so that the predetermined flow rate is not exceeded.

A total volume of pharmaceutical to be delivered to the patient in allphases is preferably determined by the parameter generation system. Inthe case of, for example, use of an unfilled container for fluiddelivery, a container from which the pharmaceutical is to be deliveredcan then be filled with a load volume of pharmaceutical based upon thedetermined total volume of pharmaceutical to be delivered by thepatient. The container can, for example, be a syringe. However, theparameter generation systems of the present invention are also suitablefor use in connection with prefilled containers (for example, syringes)or in connection with continuous or multipatient fluid delivery systemsthat can include large, bulk containers of pharmaceutical and/or agent.

In several embodiments, an initial protocol is determined by theparameter generation system to, for example, determine the total volume.The initial protocol can then be adjusted based upon a characterizationof the cardiovascular system of the patient.

A test bolus of the pharmaceutical can, for example, be performed tocharacterize the cardiovascular system of the patient. The initialprotocol can, for example, be adjusted at least in part on the basis ofa time to peak enhancement of the test bolus. In several embodiments,the initial protocol is adjusted at least in part on the basis of a timeto peak enhancement of the test bolus and a level of enhancement of thepeak enhancement.

A scan delay can, for example, be determined at least in part on thebasis of the time to peak enhancement. In one embodiment, scan delay iscalculated by the formula: scan delay=time to peak+C, wherein C is afunction of a patient parameter such as weight, body mass index, bodysurface area or cardiac output. C can, for example, be a function ofweight, body mass index, body surface area or cardiac output in the caseof scan durations of at least a predetermined time, and C can be set toa predetermined value in the case of scan durations less than thepredetermined time.

A determination can be made as to whether to adjust the ratio of thepharmaceutical to the diluent fluid in the second phase at least in parton the basis of the level of the peak enhancement.

A duration of the second phase can be calculated according to theformula: D_(DF)=Scan Delay+Scan Duration−D_(C) ^(Diag), wherein D_(C)^(Diag) is a duration of the first phase and Scan Duration is a scanduration of the imaging system. D_(C) ^(Diag) can, for example, bedetermined by adding a factor K to the scan duration of an imagingsystem. K can, for example, be in the range of approximately 0 toapproximately 10 seconds. A minimum first phase injection duration canbe input into the parameter generation system.

In another aspect, the present invention provides a system includingparameter generation system to determine parameters of at least onephase (for example, of a plurality of phases) of an injection procedurein which a pharmaceutical including an image contrast enhancement agentis delivered to a patient wherein the parameter generation systemincludes an algorithm to determine parameters based at least in partupon a type of the injection procedure, a determined time to peakenhancement and a level of peak enhancement. As used herein, the term“algorithm” refers to a procedure for determining the parameters, whichcan, for example, be embodied in software.

The time to peak enhancement and the level of peak enhancement can, forexample, be determined at least in part by an injected bolus of thepharmaceutical into a patient. The time to peak enhancement and thelevel of peak enhancement can also be determined at least in part by amodel of propagation of the pharmaceutical in a patient.

A volume of the pharmaceutical to be loaded and optionally a volume of adiluent to be loaded can, for example, be determined by determination ofinitial parameters of the injection procedure at least in part on thebasis of at least one parameter of the patient and a determined scanduration. The at least one parameter of the patient can, for example, beweight, body mass index, body surface area or cardiac output.

At least one of the time to peak enhancement and the level of peakenhancement can be used to adjust the initial parameters.

In a further aspect, the present invention provides a system including aparameter generation system to determine parameters of a diagnosticinjection protocol including at least one phase in which apharmaceutical including an image contrast enhancement agent isdelivered to/injected into a patient. The parameter generation systemincludes an algorithm adapted to determine parameters of an initialprotocol using information available prior to characterization of acardiovascular system of the patient and an algorithm to adjust theparameters of the initial protocol based at least in part on thecharacterization of the cardiovascular system to determine theparameters of the diagnostic injection protocol.

As described above, the initial protocol can, for example, be used todetermine a total volume of pharmaceutical to be injected into thepatient in all phases. A container from which the pharmaceutical is tobe delivered can be filled with a load volume of pharmaceutical basedupon the determined total volume of pharmaceutical to be delivered tothe patient. The container can, for example, be a syringe. The parametergeneration system is also suitable for use in connection with prefilledcontainers (for example, syringes) or in connection with continuous ormultipatient fluid delivery systems.

In another aspect, the present invention provides a system including aparameter generation system to determine parameters of a diagnosticinjection protocol including at least one phase in which apharmaceutical including an image contrast enhancement agent is injectedinto a patient. The parameter generation system includes an algorithm todetermine a scan delay for the patient (that is, on a per-patient orindividualized basis).

The scan delay can, for example, be determined at least in part on thebasis of the time to peak enhancement (for example, as determined duringa test injection). For example, the scan delay can be calculated by theformula: scan delay=time to peak+C, wherein C is a function of a patientparameter such as weight, body mass index, body surface area and/orcardiac output. C can, for example, be a function of a parameter such asweight, body mass index, body surface area and/or cardiac output in thecase of scan durations of at least a predetermined time, and C can beset to a predetermined value in the case of scan durations less than thepredetermined time.

In another aspect, the present invention provides system including aparameter generation system to determine parameters of a diagnosticinjection protocol including at least one admixture phase in which anadmixture including a pharmaceutical including an image contrastenhancement agent and a diluent is injected into a patient, wherein theparameter generation system includes an algorithm to determine a ratioof pharmaceutical to diluent in the at least one admixture phase for thepatient (that is, on a per-patient or individualized basis). The ratiocan, for example, be determined based at least in part upon acharacterization of the cardiovascular system of the patient. The ratiocan also be determined based at least in part upon the basis of apatient parameter such as weight, body mass index, body surface area,and/or cardiac output or upon a level of peak enhancement.

In a further aspect, the present invention provides a system asdescribed above further including at least one pressurizing mechanism;at least a first fluid container operably associated with the at leastone pressurizing mechanism, the first fluid container being adapted tocontain a pharmaceutical comprising a contrast enhancing agent to beinjected in an imaging procedure; at least a second fluid containeroperably associated with the at least one pressurizing mechanism, thesecond fluid container adapted to contain a diluent fluid; a controlleroperably associated with the at least one pressurizing mechanism, thecontroller comprising a programming system to allow programming of aninjection protocol including one or a plurality of phases. The systemcan further include an imaging system. The parameter generation systemcan, for example, be in communicative connection with at least one ofthe imaging system or the controller of the pressuring mechanism.

In another aspect, the present invention provides an injector includinga parameter generation system as described herein or of which theparameter generation system is a component.

In still a further aspect, the present invention provides an imagingsystem including a parameter generation system as described herein or ofwhich the parameter generation system is a component.

The present invention also provides method of determining parameters asset forth in the systems described above. The present invention alsoprovides parameter generation systems as described above.

The present invention, along with the attributes and attendantadvantages thereof, will best be appreciated and understood in view ofthe following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a multi-phasic Graphical UserInterface (GUI) for use in the present invention to set forth parametersfor a plurality of phases for a two-syringe injector also illustrated inFIG. 1.

FIG. 2 illustrates an embodiment of a graphical interface from which anoperator can choose a vascular region of interest for imaging.

FIG. 3 illustrates an embodiment of a graphical interface of a proposedwork flow environment for use in the present invention.

FIG. 4 illustrates an embodiment of an iodine flux algorithm for use inthe present invention.

FIG. 5 illustrates an embodiment of a weight based algorithm for use inthe present invention.

FIG. 6 illustrates an embodiment of a breath hold duration algorithm foruse in the present invention.

FIG. 7 illustrates an embodiment of a reduced-order compartmental modeland the first-order coupled differential equation system describing thismodel.

FIG. 8A illustrates a simulated enhancement curve in the heart/aorticcompartment of a 65 cm, 120 kg male.

FIG. 8B illustrates a time enhancement curve to a test/timing injectionfrom the simulated patient in FIG. 8A.

FIG. 9 illustrates a simulated time enhancement curve for the simulatedpatient of FIG. 8A using the proposed methodology described within.

FIG. 10 illustrates a time enhancement curve resulting from a 120 mluniphasic injection.

FIG. 11 illustrates a time enhancement curve resulting from a 75 mlcontrast bolus followed with a 50 ml saline push or flush.

FIG. 12 illustrates simulated time enhancement curves resulting frominjections performed with a 75 ml main bolus followed by a diluted phaseof contrast of the same flow rate having a contrast/saline ratio of50/50.

FIG. 13 illustrates simulated time enhancement curves resulting frominjections performed with a 75 ml main bolus followed by a diluted phaseof contrast of the same flow rate having a contrast/saline ratio of30/70.

FIG. 14 illustrates simulated time enhancement curves resulting frominjections performed with a 75 ml main bolus followed by a diluted phaseof contrast of the same flow rate having a contrast/saline ratio of70/30.

FIG. 15 illustrates an injection process of contrast material with afixed, time axis wherein the bottom axis presents the contrast injectionprofile, the middle axis sets forth the enhancement profiles for leftand right heart compartments, and the top axis sets forth the scanningduration.

FIG. 16 illustrates a heuristic for determining contrast/saline ratio ofan admixture or dual flow phase on the basis of peak enhancement of atest bolus.

FIG. 17 sets forth preliminary clinical data for uniphasic injections,biphasic injections and multiphasic, admixture injections of the presentinvention.

FIG. 18 illustrates several scan images of the left and right heart fora uniphasic injection, a biphasic injection and a multiphasic injectionincluding a phase in which a contrast/saline admixture is injected.

FIG. 19 illustrates an embodiment of a graphical user interface for usewith an embodiment of a parameter generator of the present invention.

FIG. 20 illustrates another portion of a graphical user interface foruse with an embodiment of a parameter generator of the presentinvention.

FIG. 21 illustrates another portion of a graphical user interface foruse with an embodiment of a parameter generator of the presentinvention.

FIG. 22 illustrates another portion of a graphical user interface foruse with an embodiment of a parameter generator of the presentinvention.

FIG. 23 illustrates another portion of a graphical user interface foruse with an embodiment of a parameter generator of the presentinvention.

FIG. 24A illustrates PB PK simulation results using Table 1 weightfactors set forth below with 370 mgI/ml contrast with a 6 ml/s flow ratelimit (13 sec scan duration).

FIG. 24B illustrates PB PK simulation results using Table 1 weightfactors set forth below with 320 mgI/ml contrast with a 6 ml/s flow ratelimit (13 sec scan duration).

FIG. 24C illustrates enhancement profiles in left heart (L) and rightheart (R) compartments generated via PB PK simulation results usingTable 1 weight factors set forth below with 370 mgI/ml contrast and a 6ml/s flow rate limit (12 sec scan duration), wherein the vertical linesindicate the scanning window as determined by the scan delay computationdescribed within and a 13 second scan duration.

FIG. 24D illustrates enhancement profiles in left heart (L) and rightheart (R) compartments generated via PB PK simulation results usingTable 1 weight factors set forth below with 320 mgI/ml contrast and a 6ml/s flow rate limit (12 sec scan duration), wherein vertical linesindicate the scanning window as determined by the scan delay computationdescribed within and a 13 second scan duration.

FIG. 24E illustrates a table of contrast loading results using valuesset forth in Table 1 and the dual flow loading coefficient.

FIG. 24F illustrates a table of total contrast volume, including a 20 mltest bolus.

FIG. 24G illustrates a table of total Iodine dose for loaded contrastvolumes, including a 20 ml test bolus.

FIG. 25 illustrates Fick's principle.

FIG. 26 illustrates an embodiment of a clinical workflow of the presentinvention setting forth scanner operations, patient managementoperations and injection system operations

FIG. 27A illustrates a flowchart for an embodiment of a protocolgeneration process of the present invention.

FIG. 27B illustrates a graph of Time to reach ¾ peak on the downslope ofa time enhancement curve as a function of cardiac output.

FIG. 28 illustrates a schematic of representative timing for a CTA (CTAngiography) procedure.

FIG. 29 illustrates raw data from a clinical trial for 20 patientswherein the y-axis is the actual volume of contrast used in the dilutionphase and the x-axis is the weight of the patients in the sample (inlbs).

FIG. 30 illustrates a Monte-Carlo simulation using biometrics for 70patients that computed diagnostic and dilution contrast protocols usinga preloaded volume.

FIG. 31 illustrates a functional description of an embodiment of aprotocol adjustment function that applies changes to the injectionprotocols based on features of a test bolus enhancement.

FIGS. 32A and 32B illustrate an embodiment of a process for adjustingvolumes, when applicable

FIG. 33A illustrates the workflow diagram of FIG. 26 in which a patientweight input step is encircled with circle A and a correspondinggraphical user interface in which patient weight can be selected from aplurality of weight ranges.

FIG. 33B illustrates the workflow diagram of FIG. 26 in which a contrastconcentration input step is encircled with circle B and a correspondinggraphical user interface in which contrast concentration is selectedfrom a plurality of available choices.

FIG. 33C illustrates the workflow diagram of FIG. 26 in which thesyringe loading step is encircled with circle C and a correspondinggraphical user interface or screen display in which the calculatedcontrast syringe and saline syringe load volumes are set forth for theuser/clinician.

FIG. 33D illustrates the workflow diagram of FIG. 26 in which the stepof data transfer from a scout scan to the protocol generation interfaceof the present invention is encircled with circle D and a correspondinggraphical user interface for entering scan duration.

FIG. 33E illustrates the workflow diagram of FIG. 26 in which an initialdiagnostic protocol computation step is encircled with circle E and acorresponding graphical user interface wherein the user is prompted tohave the protocol generation system generate the protocol.

FIG. 33F illustrates the workflow diagram of FIG. 26 in which the datatransfer step of data from a test bolus to the protocol generationinterface is encircled with circle F and a corresponding graphical userinterface for manual data entry of the time to peak and peakenhancement.

FIG. 33G illustrates the workflow diagram of FIG. 26 in which the pointat which the determination of diagnostic protocol has been completed bythe protocol generation interface and the diagnostic injection can beinitiated is encircled with circle G and a corresponding graphical userinterface setting forth the computed diagnostic protocol.

FIG. 34A illustrates an embodiment of another graphical user interfacefor use in connection with the present invention and a representation ofan ideal contrast injection with relationship to a scan

FIG. 34B illustrates volumetric flow rates and iodine administrationrates for a contrast only phase (phase 1) and a dual flow or admixturephase as determined by an embodiment of a protocol generation process ofthe present invention.

FIG. 35A illustrates results obtained using a protocol generated by aprotocol generation process of the present invention as compared to theresults obtained using a uniphasic protocol, a biphasic protocol and afixed dual flow protocol.

FIG. 35B illustrates enhancement results obtained in the descendingaorta using a protocol generated by a protocol generation process of thepresent invention as compared to the results obtained using a biphasicprotocol.

FIG. 35C illustrates enhancement results obtained in the right ventricleusing a protocol generated by a protocol generation process of thepresent invention as compared to the results obtained using a biphasicprotocol.

FIG. 36A illustrates CTA scan results obtained using a protocolgenerated by a protocol generation process of the present invention fora 139 pound female subject.

FIG. 36B illustrates CTA scan results obtained using a protocolgenerated by a protocol generation process of the present invention fora 202 pound male subject.

FIG. 37 illustrates a summary of answers provided by two blinded readersto the questions: “For this patient's intended diagnosis, do you believethat the contrast medium delivery protocol was sufficient to visualizeanatomy and diagnose pathology?” for a study group in which the protocolwas determined using a parameter generation system of the presentinvention and for a control group in which a standard protocol was used.

FIG. 38 illustrates a graphical representation of ratings by two blindedreaders of the imaging achieved by each of a contrast medium deliveryprotocol generated using a parameter generation system of the presentinvention (study group) and a standard contrast medium delivery protocol(control group) for left coronary imaging wherein a rating or “1”corresponds to the conclusion that the structure in question was notvisualized, a rating of “2” corresponds to a conclusion that thestructure in question is faintly visualized, a rating of “3” correspondsto a conclusion that the structure in question is faintly visualized anddelineation is limited, a rating of “4” corresponds to a conclusion thatthe structure in question is visualized and complete delineation ispossible, a rating of “5” corresponds to a conclusion that the structurein question is excellently visualized and delineation is excellent.

FIG. 39 illustrates an analysis similar to that of FIG. 39 for rightcoronary imaging.

FIG. 40 illustrates mean attenuation achieved for imaging of variousregions of interest for a contrast medium delivery protocol generatedusing a parameter generation system of the present invention (studygroup).

FIG. 41 illustrates mean attenuation achieved for imaging of variousregions of interest for a standard contrast medium delivery protocol(control group).

FIG. 42 illustrates mean attenuation achieved for various regions ofinterests (coronary arteries) for each of a standard contrast mediumdelivery protocol in which 70 ml of contrast medium (Ultravist 370,Schering) were injected with a flow-rate of 5.0 ml/s (Group 1) and acontrast medium delivery protocol generated using a parameter generationsystem of the present invention (Group 3).

FIG. 43 illustrates mean attenuation achieved for various regions ofinterests (coronary arteries) for each of a standard contrast mediumdelivery protocol in which 80 ml of contrast medium were injected with aflow-rate of 6.0 ml/s (Group 2) and a contrast medium delivery protocolgenerated using a parameter generation system of the present invention(Group 3).

FIG. 44 illustrates mean attenuation achieved for various regions ofinterests (left and right ventricles) for each of a standard contrastmedium delivery protocol in which 70 ml of contrast medium (Ultravist370, Schering) were injected with a flow-rate of 5.0 ml/s (Group 1) anda contrast medium delivery protocol generated using a parametergeneration system of the present invention (Group 3).

FIG. 45 illustrates mean attenuation achieved for various regions ofinterests (left and right ventricles) for each of a standard contrastmedium delivery protocol in which 80 ml of contrast medium were injectedwith a flow-rate of 6.0 ml/s (Group 2) and a contrast medium deliveryprotocol generated using a parameter generation system of the presentinvention (Group 3).

FIG. 46 illustrates a graphical representation of the volume of contrastmedium injected in two phases of injection (a contrast medium onlyphase—volume A—and a dual flow phase—volume A/B) for each of Group 1,Group 2 and Group 3.

FIG. 47 illustrates mean contrast enhancement in five coronary segmentsacross 32 subjects for another study of a parameter generation system ofthe present invention.

FIG. 48 illustrates mean contrast enhancement in four locations of theright and left ventricles.

DETAILED DESCRIPTION OF THE INVENTION

As used herein with respect to an injection procedure, the term“protocol” refers to a group of parameters such as flow rate, volumeinjected, duration etc. that define the amount of fluid(s) to bedelivered to a patient during an injection procedure. Such parameterscan change over the course of the injection procedure. As used herein,the term “phase” refers generally to a group of parameters that definethe amount of fluid(s) to be delivered to a patient during a period oftime (or phase duration) that can be less than the total duration of theinjection procedure. Thus, the parameters of a phase provide adescription of the injection over a time instance corresponding to thetime duration of the phase. An injection protocol for a particularinjection procedure can, for example, be described as uniphasic (asingle phase), biphasic (two phases) or multiphasic (two or more phases,but typically more than two phases). Multiphasic injections also includeinjections in which the parameters can change continuously over at leasta portion of the injection procedure.

In several embodiments of the present invention, an injection system(such as a dual syringe injector system 100 as illustrated in FIG. 1 andas, for example, disclosed in U.S. Pat. No. 6,643,537 and Published U.S.Patent Application Publication No. 2004-0064041) for use with thepresent invention includes two fluid delivery sources (sometimesreferred to as source “A” and source “B” herein; such as syringes) thatare operable to introduce a first fluid and/or a second fluid (forexample, contrast medium, saline, etc.) to the patient independently(for example, simultaneously, simultaneously in different volumetricflow proportion to each other, or sequentially or subsequent to eachother (that is, A then B, or B then A)).

In the embodiment of FIG. 1, source A is in operative connection with apressurizing mechanism such as a drive member 110A, and source B is inoperative connection with a pressurizing mechanism such as a drivemember 110B. The injection system includes a controller 200 in operativeconnection with injector system 100 that is operable to control theoperation of drive members 110A and 110B to control injection of fluid A(for example, contrast medium) from source A and injection of fluid B(for example, saline) from source B, respectively. Controller 200 can,for example, include a user interface comprising a display 210.Controller 200 can also include a processor 220 (for example, a digitalmicroprocessor as known in the art) in operative connection with amemory 230. Imaging system 300 can, for example, be a CT system, aMagnetic Resonance Imaging (MRI) system, an ultrasound imaging system, aPositron Emission Tomography (PET) system or another imaging system. Theinjection system can be in communicative connection with imaging system300 and one, a plurality or all the components of the injection systemand imaging system 300 can be integrated.

In several embodiments of the present invention, phase variables orparameters as described above are populated within a phase programmingmechanism (see FIG. 1 for an embodiment of a user interface thereforthat can, for example, be used with injector system 100) based on one ormore parameters of interest, including, for example, but not limited to,contrast agent concentration (for example, iodine concentration in thecase of a CT procedure), a patient parameter (for example, body weight,height, gender, age, cardiac output, etc.) the type of scan beingperformed, and the type of catheter inserted into the patient forintravascular access. As discussed above, differences in dosingrequirements for different patients during imaging and other procedureshave been recognized. For example, U.S. Pat. Nos. 5,840,026 and6,385,483, assigned to the assignee of the present invention, thedisclosures of which are incorporated herein by reference, disclosedevices and methods to customize the injection to the patient usingpatient specific data derived before or during an injection. Likewise,PCT International Patent Application No. PCT/US05/41913, entitledMODELING OF PHARMACEUTICAL PROPAGATION, filed Nov. 16, 2005, claimingthe benefit of U.S. Provisional Patent Application Ser. No. 60/628,201,assigned to the assignee of the present invention, the disclosures ofwhich are incorporated herein by reference, also discloses customizationof injections to a patient using patient specific data and sets forth anumber of models to describe a time enhancement output for a given inputor protocol.

Because optimal sets of flow rates and volumes are not readily known tothe operator of the injector, the present invention eases the task of anoperator in, for example, scanning patients in an imaging procedure byproviding a set of injection protocols that are predetermined as beingeffective for the type of procedure being performed. For example, suchprotocols can be established in the clinical literature, established bycollection of patient data over time (by, for example, employingartificial intelligence techniques, statistical means, adaptive learningmethodologies, etc.), established through mathematical modeling orotherwise established for a type of procedure being performed.

The operator can, for example, first choose the concentration ofcontrast agent (for example, concentration of iodine in a CT procedure)to be delivered into a patient. This choice is made, for example, by aselection mechanism, or by direct input of numerical values on thegraphical user interface. The clinical operator can also select thegauge of the catheter inserted into that specific patient. Catheter sizecan be entered so that in subsequent steps, when the volumetric flowrate is determined, the pressure head to be developed in a disposablefluid path set can be calculated as described below (for example, via acomputer program). Alternatively, one or more sensors can be provided tosense catheter size and provide this information to the injector.

The clinical operator can, for example, control the injection system byeither entering volumes and flow rates manually into the fields providedon the User Interface (see FIG. 1) or by entering a “protocol wizard orgeneration mode”, “helper mode” or “operator assist mode” as describedherein. In an operator assist mode, such fields are automaticallypopulated. If the operator chooses to enter the operator assist mode,the operator can be presented with a mechanism or mode (see, forexample, FIG. 2) of selecting an organ or vascular system to be scanned.

The present invention provides systems, devices and methodologies oralgorithms that predict the flow rate profile (which can be constant orvarying during a phase) and volume of contrast agent to deliverdepending upon the procedure and the region of interest chosen. Forexample, an operator can choose the heart, descending aorta or ascendingaorta (referred to as cardiac imaging, a form of Computed TomographyAngiography (CTA)). One embodiment of a graphical interface from whichthe operator chooses the vascular region of interest, and which followsthe work flow described herein, is depicted in FIG. 2. The operator can,for example, choose a region of interest by highlighting (for example,using a touch screen or a mouse controlled cursor) a region of intereston an illustration of the body set forth on the user interface or canchoose a region of interest from a menu such as a pull down menu.Hierarchical groupings of regions of interest can be provided.

In addition to use of the injector system to affect the above-identifiedchoices, the choices set forth above can also or alternatively be madeon a user-interface on the imaging system or scanner and/or from adatabase on the imaging system or scanner. In the case that the choicesare made via an interface or database resident on the scanner, the datacan then be transmitted to the injector. Moreover, the interface canexist solely on the scanner/imaging system. In this case, the finalprotocol can be transmitted to the injection system. Likewise, theinterface or database can exist on a machine or system separate from theinjector and the scanner. Data (for example, protocols) can betransmitted from that system to the injector. A communication interfacethat may be used herein is disclosed in U.S. Pat. No. 6,970,735, thecontents of which is incorporated herein by reference.

Upon choosing the region to be imaged, the operator can, for example, beprompted to enter values for other variables (for example, patientphysiological variables such as the patient's weight, height, gender,etc.). An example of an embodiment or implementation of this is toprovide a keypad on the user interface into which the operator entersthe patient's weight in pounds or kilograms. In another embodiment, theoperator chooses a weight range from among low, mid and high ranges.Such variables can also be measured by one or more sensing devicesassociated with the system and/or read electronically or digitally frompatient records as may be kept in a hospital database. The stepsnecessary to conduct a contrast injection can be presented to theoperator as depicted in FIG. 3. In the embodiment of FIG. 3, theoperator can, for example, be prompted in an order (for example, asuggested or required sequential order) natural to the type of imagingprocedure to be performed. The operator can, for example, be given theability to choose a vascular region or organ of the body to image, thetype of algorithm to conduct the injection, and an ability to change thetype of contrast, catheter gauge, and/or physical attributes of thepatient.

As discussed above, the operator can be presented with a choice of thetype of algorithm the operator would like the system to use to produce aset of flow rates and volumes (that is, phase parameters) for thatpatient. In the case of cardiac imaging, algorithm choices can, forexample, include: (i) an Iodine Flux Algorithm, (see FIG. 4) (ii) aWeight Based Algorithm (see FIG. 5), (iii) a Breath Hold DurationAlgorithm (see FIG. 6) or (iv) a “Cardiac” algorithm (see FIGS. 24Athrough 35B) or other body region specific algorithm. One or more ofthese algorithms can, for example, be based upon empirical data (forexample, as published in the radiological medical literature).Additional algorithms can be included for other types or classes ofimaging procedures. The methodologies and/or logic for embodiments ofthe four algorithms described above are set forth in FIGS. 4, 5, 6, and24A through 35B, respectively. Upon entering the data required for aparticular algorithm, the operator can be queried if the operator wishesto perform a test injection (or timing injection). If the operatorchooses yes, the software can provide that, for example, two additionalphases (corresponding to the test injection) must be inserted in thestart of the injection protocol (for example, one phase for contrastdelivery and a subsequent phase for a saline flush injection).

Based upon the selections made, the software implementing the presentinvention computes an injection protocol for the user's review. If theoperator chooses to perform a test injection, then the first two phasesof the protocol can, for example, include injection of 15 or 20 ml ofcontrast agent (for example, 15 ml if the patient weight <90 kg, 20 mlif the patient weight >90 kg) delivered at 4 ml/s. The second phase ofthe protocol can include injection of 20 ml of saline injected at 4ml/s. The next phase or phases can, for example, include volumes andflow rates computed by one of the four algorithms discussed above or oneor more other algorithms.

In a number of embodiments of the present invention, injectionparameters for an injection procedure including a phase in which anadmixture of contrast media and a diluent/flushing fluid (for example,saline) are calculated. In that regard, to address a number of problemsassociated with, for example, heart imaging, procedures have beendeveloped which include the injection of saline following the contrastagent bolus, and, more recently, the admixture of contrast media withsaline via simultaneous injection of contrast media and saline(sometimes referred to herein as “dual flow”).

As discussed above, one proposed solution to non-uniform enhancementproblems is injection of contrast with an exponentially decaying flowrate over time. While this technique can indeed produce more uniformcontrast enhancement in a large vessel, it also reduces the maximumenhancement, which is not necessarily desirable. While, theoretically,it seems logical to believe that the exponentially decaying flow ratescan help with right-heart artifacts (for example, by introducing lesscontrast later in the injection and mixing less with the earlierinjected contrast), it has not been demonstrated or investigated.Furthermore, because the latter portion of the decayed injection is at alower flow rate, there is a loss of momentum for that section of thebolus, slowing its entry to the right heart. While a saline push afterthe decayed exponential injection may help in ensuring the contrast isall “pushed” into the right heart, turbulence resulting from the mixingof contrast and blood at different flow rates may cause flow artifactwithin the right heart.

An alternative for reducing right heart artifact is to inject a volumeof contrast at a discrete flow rate followed by an admixture of contrastand saline (with a final push of saline). The admixture can be injectedat the same flow rate as the initial bolus of contrast. The admixturecan be produced by the simultaneous injection of contrast and salinewith, for example, a dual-syringe power injector, wherein the flow ratesof contrast and saline are proportional to each other. This techniquehas been recently adopted in the clinical setting and initial resultssuggest that it reduces right heart artifact. However, in implementingsuch admixture protocols, there are currently no established systems ormethods for determining appropriate or ideal injection parameters for agiven patient (for example, initial flow rate and volume, percentage ofadmixture, duration of the phases, and scan delay).

In several embodiments, the present invention provides systems andmethods for interfacing with the injection system to reduce clinician“guesses” at appropriate or optimal flow rate and volume parameters fora given patient. The systems and methods of the present inventionprovide for the consideration of a number of variables including, butnot limited to, patient specific parameters such as patient weight (andother habitus indicators such as height, cardiac output, etc.), time ofcontrast arrival from a timing injection, contrast concentration, andtotal desired contrast agent (for example, iodine) load. The systems andmethods of the present invention can, for example, include a per-patientsaline admixture protocol generator.

The predicted contrast enhancement in the aortic/heart compartment of ahuman male can be used in this section to elaborate the principle of theproposed algorithm. In several studies, simulations were performed in aSIMULINK® (available from MathWorks, Inc. of Natick Mass.)implementation of a full body, Physiologic Based Pharmacokinetic Model(PBPK) PK model as described in Bae et al. See Bae, K. T., J. P. Heiken,et al., “Aortic and hepatic contrast medium enhancement at CT. Part I.Prediction with a computer model,” Radiology 207(3): 647-55 (1998), andBae, K. T., H. Q. Tran, et al., “Multiphasic injection method foruniform prolonged vascular enhancement at CT angiography:pharmacokinetic analysis and experimental porcine model,” Radiology216(3): 872-80 (1998); U.S. Pat. Nos. 5,583,902, 5,687,208, 6,055,985,6,470,889 and 6,635,030. The modeling approach in that work recognizedthat the full body physiologic pharmacokinetic model taught in Bae,Heiken et al, 1998 supra, was too large and included too many unknownsto feasibly compute on a per patient basis. Bae and colleagues,therefore, approximated large parts of the anatomy with singlecompartments and, because first-pass enhancement dynamics are ofinterest, removed the capillary transfer compartments. The resulting,reduced-order model is illustrated in FIG. 7. In FIG. 7, V are the fluidvolumes of the respective “compartments”, C are the predictedconcentrations in each “compartment”, and Q are the volumetric flowrates of blood throughout the body. Q and V are estimated fromanatomical data. The first-order, coupled differential equation systemdescribing this model is formulated assuming a continuous time processand is also set forth in FIG. 7.

In several studies of the present invention, an assumption was made thatthe aortic/heart compartment was well mixed. Although the x-axes inFIGS. 8A through 9 are labeled in time units, another assumption wasthat the time axis maps to spatial dimensions in the compartment ofinterest. FIG. 8A demonstrates the phenomenon of non-uniform contrastenhancement (caused by recirculation of contrast into the compartment).FIG. 8B presents the results of performing a small volume “test” or“timing” injection on the same patient scanned in connection with FIG.8A (the cardiac output and central blood volume for the model werederived from anthropometric data tables). The time to peak contrastenhancement was measured as 12 seconds in FIG. 8B. The time of peakrepresents the transit time for a small bolus of contrast to migratefrom the injection site, to the right heart, through the pulmonarycirculation, and to the left heart compartment. The simulated time topeak enhancement may be less than that from a “real” patient. In thatregard, the model set forth in FIG. 7 was not directly validated withhuman data, but was allometrically scaled from porcine data. In anyevent, the absolute values in these simulations are not critical.Rather, we are interested in the dynamics of the system. Noticeable inFIG. 8B is the recirculation of contrast after the peak (or firstmoment) of the bolus arrived in the compartment (>15 sec). Thereduced-order model set forth in FIG. 7 does not reproduce with highfidelity the recirculation dynamics (for example secondary peaks).

Previous studies have concluded that if an injection duration is longerthan the time for contrast arrival as computed from a timing injection,that the time to peak contrast enhancement increases linearly as theduration of injection increases. As the duration of the injectionexceeds the duration of the time to peak of the test injection, theasymmetry of the enhancement curve becomes pronounced because the newcontrast is mixing with the contrast already present in the compartment.This phenomenon serves as a basis of one embodiment of one algorithm ofthe present invention for computing admixture protocol (for example,saline plus contrast media).

FIG. 9 sets forth a time enhancement curve that was simulated with abiphasic protocol. The first phase's duration was computed to equal thetime to peak enhancement of the timing bolus, plus three seconds (anarbitrary offset term). The second phase was a diluted phase (90%contrast, 10% saline) that resulted in an effective contrastconcentration of 288 mgI/ml (concentration in the dilution phase=desiredor programmed ratio (90/100 in this instance)* concentration of drug(320 mgI/ml)). The volume was set so that a total volume of 120 ml wasinjected into the patient. The flow rate was the same in both phases tomaintain the momentum of the contrast into the right heart. FIG. 9demonstrates a reduction in the asymmetric “peak” in the second half ofthe injection, while maintaining a contrast enhancement about 350 HU. Incomparison, an exponentially decreasing flow rate technique results in alower peak enhancement. An advantage of the injection protocol of thepresent invention (as compared to a decelerating injection flow rateprotocol) arises in that, because the volumetric flow rate of theinjected fluid is not decreasing, there is less likelihood for flowartifacts within the peripheral venous system before the heart. In thatregard, injectate moving with a flow rate less than the endogenous flowrate of the venous system can result in dispersion of the contrast mediabecause some parts of the bolus arrive to the right heart with differentvelocities. In the present invention, a multiphasic injection protocolcan be provided in which one or more of the parameters are changedperiodically or continuously over at least a period of the injectionduration, wherein total flow rate is maintained constant. In thismanner, for example, a concentration of contrast active agent (forexample, iodine, gadolinium, etc.) delivered to a patient can bedecreased over time while maintaining flow rate constant (for example,by increasing the portion of saline injected during that time). Abroader, more uniform peak of enhancement can thereby be maintained(see, for example, FIG. 9). Moreover, that uniformity can be changedbetween different phases of the injection procedure. For example, liverenhancement can be changed during different phases of the imagingprocedure to, for example, correspond to different portions of the liverin which peak enhancement time can vary because of variations in bloodsupply.

Another embodiment of the present invention for protocol determinationor parameter generation in the case of a dual flow injection orsimultaneous injection of an admixture of diluent/flushing fluid andcontrast is discussed in connection with FIGS. 10 through 18. Onceagain, a primary goal of rational CT contrast protocol design is todevelop injection protocols tailored to each patient considering, forexample, the individual's hemodynamic state, the imaging region ofinterest, and the injection system constraints. The injection strategycan, for example, make use of the ability of the STELLANT® D injectionsystem, available from Medrad, Inc. of Indianola, Pa., to providesimultaneous delivery (and thus dilution) of contrast media and saline.As described below, an additional phase of diluted contrast media allowsfor additional left heart enhancement, but with a reduced contrast agent(iodine) load to reduce or eliminate right heart artifacts.

FIGS. 10 thorough 14 illustrated enhancement profiles (simulated asdescribed above) for a 35 yr old, healthy male (200 lbs, 6 ft tall)injected with 370 mgI/ml contrast medium. Enhancement curves arepresented for the right heart and the left heart compartments aspredicted with the compartmental, pharmacokinetic model set forth inFIG. 7. FIG. 10 depicts enhancement with a 120 ml uniphasic injection,whereas FIG. 11 presents the enhancement resulting from a 75 ml bolusfollowed with a 50 ml saline push or flush. Whereas the enhancement ofthe left heart in FIG. 10 is above 300 Hounsfield Units (HU) throughoutthe scan duration, the right heart is enhanced brightly throughout thescan window, and is more likely to produce image artifacts.

FIGS. 12-14 illustrate simulated time enhancement curves resulting frominjections performed with a 75 ml main bolus followed by a diluted phaseof contrast of the same flow rate in the following contrast/salineratios: 50/50, 30/70, and 70/30, respectively. The enhancements of theleft and right hearts were clearly modified by the additional phase ofdiluted contrast. The 70/30 phase (FIG. 14) provided good left heartenhancement, but the right heart enhancement may have been too great.The 30/70 ratio (FIG. 13) provided good right heart enhancement, but notenough left heart enhancement throughout the scan window. The 50/50ratio (FIG. 12) provides the best trade-off, for this simulated patient,of right heart and left heart enhancement.

FIG. 15 illustrates an injection process of contrast material with afixed, time axis. The bottom axis presents the contrast injectionprofile (in this instance, a uniphasic injection at 5 ml/s), the middleaxis sets forth the enhancement profiles for left and right heartcompartments, and the top axis presents the scanning duration. The twovertical lines represent the start and completion times of the scan. Inone embodiment, an algorithm of the present invention assumes that theclinician performs a small, test bolus injection of contrast (forexample, a test injection of 20-25 ml of contrast at the same flow rateas the flow rate to be used during the diagnostic scan) followed by asaline push. A dynamic CT scan generates an enhancement curve from whichthe time to peak of the test bolus and the enhancement peak of the testbolus can be measured/recorded. It is also assumed that the scanduration is known before the test bolus and diagnostic injections begin.

In one embodiment, the first bolus of contrast is made equal in durationto the scan duration. The flow rate is given by the operator (assumed tobe 5 ml/s in this study). The volume of the first phase, therefore, isthe product of scan duration and flow rate. The determination of thevolume of the second phase is made by considering the time to peak ofthe test injection, the duration of the first phase, and the end of thescan. The contrast injection should not last longer than the end of thescan. Because of the propagation delay of contrast from the injectionsite to the right atrium (about 5-8 seconds typically), contrastinjection is stopped 5-8 seconds before the end of the scan so that thefollow on contrast can fill the right heart. The approach taken inconnection with the embodiment of FIG. 15 proscribed a saline flush of40 ml at 5 ml/s, so the contrast injection of the dilution phase wasended 8 seconds before the end of the scan.

The volume of the second, diluted phase is then determined by:

${Vol}_{2} = {{\left( {\left( {t_{scan\_ end} - \frac{40\mspace{11mu}{ml}}{5\mspace{11mu}{ml}\text{/}s}} \right) - {duration}_{1}} \right) \cdot 5}\mspace{11mu}{ml}\text{/}s}$The value T_(scan) _(_) _(end) is computed by consideration of the timeto peak of the test bolus and the scan duration:t _(scan) _(_) _(end) =t _(test) _(_) _(bolus) _(_)_(peak)+duration_(scan)The ratio of the second phase is determined by a heuristic that mapspeak enhancement of the test bolus to contrast/saline ratio as set forthin FIG. 16.

To limit the total amount of contrast delivered to each patient (in theevent of an extremely long time to peak of the test enhancement), amaximum of 40 ml is made available for the dilution phase. If thecomputations above suggest a contrast volume greater than 40 ml., thesystem can limit the total contrast volume to 40 ml, compute the totalvolume in that phase (with the saline) considering the dilution ratio soas not to exceed 40 ml of contrast. The total contrast volume allowablein the dilution phase can also be set as a function of weight, estimatedor measured cardiac output, Body Mass Index, or other physiometricindicator. Bioimpedance measurements have been developed tonon-invasively measure cardiac output. The BIOZ® system available fromCardioDynamics International Corporation of San Diego, Calif. can, forexample, be used to measure a patient's cardiac output via impedancecardiography. Impedance cardiography (ICG), also known as thoracicelectrical bioimpedance (TEB), is a technology that converts changes inthoracic impedance to changes in volume over time. In this manner,impedance cardiography is used to track volumetric changes such as thoseoccurring during the cardiac cycle. Such measurements are gatherednoninvasively and continuously. In general, an alternating current istransmitted through the chest. The current seeks the path of leastresistance: the blood filled aorta. Baseline impedance to current ismeasured. Blood volume and velocity in the aorta change with eachheartbeat. Corresponding changes in impedance are used with ECG toprovide hemodynamic parameters. See Overview of Impedance Cardiographyavailable at http://www.impedancecardiography.com/icgover10.html andwww.cardiodynamics.com.

The threshold values in FIG. 16 were determined by analyzing clinicaldata from a sample of 50 test bolus injections and subsequent numericalmodeling. Heuristically, the rule is designed to provide more contrastin patients with smaller peak enhancements (assuming that more contrastis needed for sufficient left and right heart enhancement) and lesscontrast to patients with strong test enhancements. Because the volumeof agent is being tailored to patients with longer or shorter times topeak, and the total iodine load is adjusted based on test bolusenhancement, variability among patient enhancement should be reducedwith this approach. FIG. 17 sets forth preliminary clinical dataindicating this outcome. In FIG. 17, the first 2 bars are data generatedwith the algorithm just described for the left and right heart (SF_L andSF_R, respectively). The error bars indicate +/−1 standard deviation.The remaining data points are enhancement values generated with auniphasic protocol of 120 ml of contrast (350 mgI/ml, no saline push;UNI_R and UNI_L), a biphasic protocol (75 ml of 350 mgI/ml with 40 ml ofsaline; BI_R and BI_L), and finally a dilution protocol with a fixeddilution ratio of 30/70 for all subjects (initial phase volume of 350mgI/ml=scan duration*5 ml/s; DF_R and DF_L). The volume of the secondphase was a fixed 50 ml of fluid. A saline flush of 40 ml followed.

FIG. 18 sets forth scan images for the left and right heart in the caseof a uniphasic or monophasic injection protocol (contrast only, nosaline flush), a biphasic protocol (contrast followed by a saline flush)and a dual flow injection protocol as described above (contrast,followed by a contrast/saline admixture, followed by a saline flush). Asillustrated in FIG. 18, a dual flow injection procedure in which theinjection protocols can be determined as described above can provideimproved imaging procedures for the left and right heart.

FIGS. 19 through 23 illustrate several screen captures of a graphicaluser interface suitable to effect the dual flow injection protocoldetermination described above. In FIGS. 19 and 20 the algorithm setforth above in connection with FIGS. 10 through 18 is selected via thedesignation Cardiac CT1. A patient weight of 65 kg and a test scanduration of 30 seconds are input. An iodine flux of 1.0 g/s isestablished for the imaging procedure injection. As the concentration ofcontrast fluid is 250 mgI/ml, a flow rate of 4 ml/s will be used in theimaging procedure injection.

As set forth in FIG. 21, the flow rate during the test injection is 1.0ml/s. During the 30 second test injection, a bolus of saline (fromsource B) is first injected at a flow rate of 4.0 ml/s for 5 seconds. Abolus of contrast (from source A) is then injected at a flow rate of 4.0ml/s for 5 seconds. Finally, a flushing bolus of saline is injected at aflow rate of 4.0 ml/s for 20 seconds. After the completion of the testbolus injection, the time to peak and the peak enhancement aredetermined as illustrated in FIG. 22. Using the values set forth above,the diagnostic injection protocol is determined using the system/methoddescribed in connection with FIGS. 10 through 18. FIG. 23 sets forth thedetermined diagnostic injection protocol including the following threephases: (1) injection of a 70 ml volume of contrast (source A) at 4 ml/s(duration of 18 seconds); (2) injection of a 35 ml volume of a 50/50contrast/saline admixture (dual flow from sources A and B) at 4 ml/s(duration of 9 seconds); and (3) injection of an 80 ml volume of saline(source B) at 4 ml/s (duration 20 seconds). Thus, a total of 185 ml offluid is injected over a time period (total duration) of 47 seconds. Asalso set forth in FIG. 23, a pressure limit of 300 psi for the fluidpath used in the injection procedure was set. Also, a scan delay of 5seconds was established.

Other embodiments of protocol generation or determination systems,devices and methods (sometimes referred to collectively as systems) ofthe present invention are described below. As described above, theprotocol generation systems provide an injection protocol that isadapted or personalized for a specific patient. In several embodiments,an initial protocol, including parameters for one, two or more phases,is determined based upon available information (for example, one or morepatient parameters such as weight, height, cardiac output, etc.,concentration of an agent in the pharmaceutical to be delivered—forexample, a contrast enhancing agent such as iodine—scan duration, etc.).This initial protocol can, for example, be used to determine a volume ofpharmaceutical, a diluent (for example, saline), and/or other fluid tobe delivered to the patient, which, in turn, can provide volumes of suchfluids to be loaded into containers (for example, syringes) from whichthe fluid will be delivered. Several representative embodiments ofinjection of contrast using fillable syringes are set forth below toillustrate the present invention. In such procedures, a clinician mustpreload the syringe(s) with a volume of contrast prior to, for example,performing a test or identification bolus. It is impractical (at leastwith the current generation of injection systems) to expect theclinician to load or reload contrast into the syringe after theidentification bolus has been performed. The protocol determinationstrategies of the present invention enable a priori determination ofdoses/volumes that the clinician then loads.

After determination of an initial protocol and loading of thesyringe(s), an identification bolus or test bolus can be administered tothe patient as described above. Once again, the identification or testbolus is a low volume injection of contrast. A single level scan can,for example, be performed in a region or territory of interest in, forexample, the cardiac vasculature. The morphology of the resultingenhancement curve gives insight to the characteristics of thecardiovascular system and the dynamics of propagation of the agent ofinterest in the pharmaceutical (the contrast) in situ, from whichtailored or adjusted injection protocols can be generated.

1.0 Design Description

In a representative embodiment, the primary data used to compute thevolume of contrast to be delivered/loaded were the scan duration, one ormore patient parameters such as the patient's weight, and contrastconcentration.

A variable weighting factor (mg Iodine/Body weight kg) was used todetermine the dose of Iodine for the patient. In general, there is alinear relation between the plasma concentration of Iodine and theenhancement (or CT Number) in Hounsfield Units in a blood vessel. Weightis easily obtained before the patient is scanned and serves as apractical means of computing the preload volume of contrast. Therequirement to compute a preload volume can be eliminated through use ofa continuous flow system using bulk containers of, for example, contrastand a flushing fluid or diluent (for example, saline) as described, forexample, in U.S. Pat. Nos. 6,901,283, 6,731,971, 6,442,418, 6,306,117,6,149,627, 5,885,216, 5,843,037, and 5,806,519, Published U.S. PatentApplication No. 2006/0211989 (U.S. patent application Ser. No.11/072,999), and Published PCT International Patent Application No.WO/2006/096388 (PCT International Patent Application No.PCT/US2006/00703), the contents of which are incorporated herein byreference.

In several embodiments, the process software of the present inventiondiscretizes the weight ranges of subjects in, for example, 7 ranges (forexample, <40 kg, 40-59 kg, 60-74 kg, 75-94 kg, 95-109 kg, 110-125kg, >125 kg). The loading coefficients or functions for the software,which depend upon and vary with patient weights, are displayed in Table1 below. The coefficients or functions were derived by applying amulti-objective optimization routine (Gembicki's weighted goalattainment method (Gembicki, F. W., “Vector Optimization for Controlwith Performance and Parameter Sensitivity Indices,” Case WesternReserve University (1974)) to simulated patients representing each ofthe weight ranges (using the physiologic based pharmacokinetic model setforth above in FIG. 7. As clear to one skilled in the art, the loadingcoefficients or functions can also be determined using a formula. In themulti-objective optimization, a representative goal was set to attain atleast 350 HU peak enhancement in the Descending Aorta compartment of thephysiologic PK model and attain enhancement greater than 300 HU for atleast the duration of the scan. Rather than simulating and optimize allcombinations of contrast concentration and scan durations, arepresentative optimization was performed with 370 mgI/ml contrastconcentration and a 13 second scan duration—typical for cardiovascularCTA. The values reported in Table 1 were modified slightly from thosegenerated in the optimization to accommodate other concentrations usingsimulation and applying engineering judgment. The results of thesimulations are set forth in FIGS. 24A through 24G. The goals set forthabove are not explicitly recognized in the two lightest cases, whichwere allowed as a result of a desire to restrict contrast volume tosmaller patients (most likely pediatric patients).

TABLE 1 Weight Weight Weight Factor Range Syringe Permitted Value In mgof Iodine/kg In kg (200, 150, 100) In kg patient weight  <40 200, 150,100 40 0.45 40-59 200, 150, 100 50 0.40 60-74 200, 150, 100 67 0.37575-94 200, 150, 100 85 0.367  95-109 200, 150 102 0.35 110-125 200 1180.31 >125 200 125 0.30

In several embodiments, published results of previous studies were usedto provide the boundary conditions for the dosing scale of the softwareof the present invention. Previous studied indicate that a fixedinjection duration (and a flow rate computed to achieve a weighted doseof plasma Iodine) produces enhancement values (across a sample) and timeto aortic peak independent of patient habitus. Published pharmacokineticanalysis of contrast dynamics also leads to the same conclusion. Inseveral embodiments, the injection duration in the software of thepresent invention was fixed (for a patient) based on the scan durationif the computed flow rate was not greater than a clinically realizablevalue (as determined by the clinician).

Common current clinical practice calls for CTA injection protocols withdurations equal to the scan duration. This practice may achievesuboptimal results in most cases because of non-deterministic delays inthe scanner's activation. A conservative approach to protocol design (toprevent “missing” the bolus) while recognizing that contrast dispersesin the vessels is then to inject contrast with duration longer than thescan duration. In several embodiments, the protocol determinationsoftware of the present invention used a rule that the inject duration(for a patient) is the scan duration plus 4 seconds, unless the scan isless than 16 seconds, for which a minimum injection duration of 16seconds is proscribed.

Previous studies have demonstrated the linear time invariant propertiesof contrast medium propagation and enhancement. Analyses and experimentsreported in the radiological literature demonstrate that the Iodine fluxrate [mg I/s]I into the patient has a linear relationship to peak Iodineplasma concentration (and subsequently contrast enhancement). Currentpractice mandates a high plasma concentration (and enhancement value) ofIodine for robust coronary artery CTA (>=400 HU). Therefore, a highIodine input flux is desired. The input flux should be constrained,however, with the realization that contrast injection rates typicallydon't exceed 6-7 ml/s. Current cardiac 64 MSCT (Multislice CT) scandurations range from 10-20 seconds.

Recognizing that the Iodine delivery flux is computed by multiplicationof the contrast concentration [mgI/ml] by the administration flow rate[ml/s], one skilled in the art appreciates that, to achieve a high inputflux, either the concentration or the flow rate should increase. Simplepharmacokinetic theory and Fick's principle (see FIG. 25) demonstratethis idea explicitly. For the sake of appreciating CTA enhancement, onecan make a conceptual model of the enhancement mechanism by describing avolumetric flow rate input (Qi) into a well mixed compartment with aconcentration of agent (Ci). The volumetric flow rate of blood intowhich the agent is introduced is Qo (the cardiac output for aphysiological system). The governing differential equation for thissituation is given in Equation 1 below. A graphical depiction of thesingle compartment flow model is also depicted below. The solution ofthe differential equation for t<tend gives an insight to the interplayof injection rate, cardiac output, and input concentration of thespecies being introduced.

$\begin{matrix}{{V\frac{\mathbb{d}C_{o}}{\mathbb{d}t}} = {Q\left( {C_{i} - C_{o}} \right)}} & {{Equation}\mspace{14mu} 1} \\{{C_{o}( t)} = \left\{ \begin{matrix}{{\frac{Q_{i}}{Q_{o}}{C_{i}\left( {1 - {\mathbb{e}}^{{- \frac{Q_{0}}{V}}t}} \right)}t} \leq {injectDuration}} \\{{{C_{o}({injectDuration})}{\mathbb{e}}^{\frac{- Q_{o}}{V}t}t} > {injectDuration}}\end{matrix} \right\}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

Equation 2 assumes that an input function of concentration in timeextends from 0 to injectDuration seconds (a step function). Analysis ofthe solution in Equation 2 demonstrates that as Q_(i) or C_(i)increases, the concentration in the well-mixed central blood compartmentincreases (recall that the enhancement level in CTA is directlyproportional to plasma concentration of the contrast agent (1 mgI/ml=25HU at 120 kVP)). Also note that as the cardiac output (Q₀) increases,the plasma concentration and thus the enhancement level decreases (whichagrees with previous empirical porcine work and findings in humans).

Using the weighting scale proposed in Table 1 (most convenient forpreloading the syringe before the procedure) and recognizing that 7 ml/sis a practical limit for injection rates and imposing a minimumadministration rate of 1 gI/s input flux for the lowest weight class(<40 kg), a minimum injection duration of 16 seconds provides a goodtrade-off between minimizing flow rate while maximizing Iodine flux rate[mg I/s]. Pharmacokinetic modeling and previous studies suggest that anIodine administration rate of 1.75 gI/s for a 75 kg person is ideal forcardiac CTA. Ideally, the contrast protocol flow rate would bedetermined by asserting a gI/kg/s computation. However, access to scanduration at syringe load time cannot be guaranteed. The goal ofachieving 1.75 gI/s (for a 75 kg patient with 370 contrast), though, isrealized with the loading factors and injection duration rules presentedherein. Above scan durations of 16 seconds, the scan duration plus 4seconds is the rule to compute the injection duration per patient (plus6 for patients >102 kg) to ensure the injection lasts longer than thescan.

As described above, a number of commercially available injectors offerthe ability to simultaneously inject an admixture of contrast and aflushing fluid or diluent such as saline, thereby diluting the Iodineconcentration of contrast entering the patient. This approach has valuefor reducing the incidence of streaking artifact pronounced in cardiacMSCT scans caused by less dilute contrast media flooding the SuperiorVena Cava (SVC) and right heart while diluted (by the central bloodvolume) contrast previously injected is circulating through the coronarycirculation (and left heart). By reducing the Iodine concentrationduring the injection, reductions in streak artifact and more consistentopacification of the right heart is possible. In general, currentimplementations of the dilution technology on, for example, theSTELLANT® injector system available from Medrad Inc. of Indianola, Pa.,prompt the clinician to enter a ratio of contrast to saline for deliveryin injection phases. The clinician must apply judiciousness in selectingthe “proper” ratio for the patient. In several embodiments, the softwareembodying the protocol determination strategy of the present inventionattempts to rationalize the ratio of contrast to saline by choosing aratio based on the morphology of the identification (test) bolusenhancement, the diagnostic injection duration, scan delay, and scanduration. In that regard, patients with higher test enhancement peaksshould require more diluted contrast whereas those with less test bolusenhancement require less diluted contrast.

2.0 Protocol Generation Implementation

An embodiment of a clinical workflow of the present invention isillustrated in FIG. 27A. As clear to one skilled in the art, datatransfers between, for example, a scanner and an injector can occur viaan electronic communication link and/or via user input. In severalstudies, the protocol required a test bolus, required the use of, forexample, a 200 ml syringe and used a diluted contrast or admixture phasefor each patient. Calculations set forth herein use the followingnomenclature for describing the various phases of the protocol

Rate is designated by “R”;

Volume is designated by “V”; and

Duration is designated by “D”.

Subscripts indicate the type of media injected, where “C” is forcontrast, “S” is for Saline and “T” is for total for a dual flow oradmixture ratio. Superscripts indicate the portion of the protocol. Thesuperscript “TI” stands for test injection; “TB” stands for test bolus;“Diag” stands for the first phase diagnostic portion of the protocol;“DF” stands for the dual flow phase; and “Flush” stands for the lastsaline phase. For example, the following symbol represents the flow rateof the admixture, dual flow or ratio phase of the diagnostic portion ofthe protocol.R_(T) ^(DF)=4 mlThe following subsections are elaborations on the correspondinglynumbered operations described in FIG. 27A.

2.1 Computation of Diagnostic Volume

The computation of the volume to be loaded uses the patient weight todetermine the first phase and dual flow contrast volume based on theweight factor. The weight algorithm discretizes the weight range forclinical implementation ease. Table 1 sets forth the weight buckets, thevalues to use for each weight bucket and the weight factor.Alternatively, an algorithmic relationship can be set forth.

The volume calculations are based on the weight of the patient, thecontrast concentration and the options used for the calculation. Theweight factor is used for all patient based dosing calculations for theselected buckets. All weight calculations are in kilograms or kgshereafter unless specifically indicated otherwise.V _(C) ^(Diag)=weight×weightfactor×1000/concentration  Equation 3

2.2 Computation of Injection Duration

A number of studies indicate that important control parameters forsufficient, first-pass CTA enhancement include Iodine mass-flux rate(mgI/s) and the duration of the injection. In several embodiments, thesystems and methods of the present invention therefore personalize thedosage of contrast by manipulating the Iodine flux and injectionduration. The volume of contrast is a dependent parameter. The scanduration is computed by the scanner on a per patient basis dependent onscanning and physiological parameters—for example, slice width, pitch,spatial resolution, region of interest, and heart rate. Ideally theoperator has access to this data before the contrast can be loaded intothe syringe, but accommodation is made in the present invention forcases in which such data is not available a priori. Ideally theinjection duration would be equivalent to the scan duration. Because ofdiffusion, dispersion and scanning timing inaccuracies, a “safety”factor is typically needed to provide extra contrast.

The calculated injection duration of the first contrast phase is basedon the scan duration with a minimal duration. Sixteen seconds provides asufficient bolus width to account for timing inaccuracies in, forexample, MSCT systems (with or without bolus tracking software). If aguaranteed, deterministic timing mechanism existed or if the wholetiming bolus enhancement curve was available, this injection durationcould theoretically be decreased to the scan duration (or shorter). Thesystems and methods of the present invention also support the use of anidentification (that is, timing) bolus in addition to using bolustracking software as known in the art for determining scan triggeringtimes. The contrast bolus is lengthened, then, to 16 seconds for scansless than 12 seconds and a fixed duration factor “X” is added for longerscans.D _(C) ^(Diag)=maximum(16, scan duration+X) if scan duration>=20 sec D_(C) ^(Diag)=scan duration end  Equation 4

A simple pharmacokinetic analysis as described above can lend insightand rationale for choosing the “X” factor of Equation 4. Upon thecompletion of the input function (injectDuration in Equation 2), thedecay of plasma concentration follows a first-order decay.

A typical cardiac output for a human is 5 L/min, and an average CentralBlood Volume (the volume between the injection site and vascularterritory of interest) is 900 ml. Using these parameters in Equation 2,one can solve for the ½ time constant and ¾ time constants. These timesgive insight to how much the plasma concentration is decreasing postmaximal contrast enhancement in the vascular territory of interest.Equation 5 sets forth the calculations to determine the ½ and ¾ timeconstants. Given the standard Central Blood Volume, one can vary thecardiac output over the typical physiologic realm and find thecorresponding ½ or ¾ time constant value as illustrated for t_(3/4) inFIG. 27B.

$\begin{matrix}{{t_{1/2} = {{\ln({.5})} \cdot {- \frac{V_{CBV}}{Q_{CO}}}}}{t_{3/4} = {{\ln({.75})} \cdot {- \frac{V_{CBV}}{Q_{CO}}}}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

Four seconds provides an additional “safety” factor (the time to ¾enhancement is greater than even that computed for a cardiac output of4800 ml/min) for all cardiac outputs for achieving ¾ peak enhancementduring the “tail” of contrast enhancement in the vascular region.

2.3 Computation and Limiting of Flow Rate

The flow rate is the combination of the volume and the duration. Thecalculation for the flow rate for the first or contrast only phasecontrast is:R _(C) ^(Diag) =V _(C) ^(Diag) /D _(C) ^(Diag)  Equation 6R_(Total) ^(DF)=R_(C) ^(Diag)  Equation 7R_(C) ^(TB)=R_(S) ^(TB)=R_(C) ^(Diag)  Equation 8

The volumetric flow rate computed by Equation 6 is applied to all phasesof the protocol (timing bolus, saline flush, dual flow, etc.).

2.3.1 Flow Rate Limiting

A site may choose to limit the maximum flow rate to a patient, or to allpatients. Such an option can, for example, be a system configurationoption. To deliver the maximum volume of the preloaded contrast, theduration of the first phase can, for example, be allowed to extend intime but only to a preset time (for example, 22 seconds). Additionalcontrast volume at the clamped flow rate will not be delivered. Theclamping of the injection duration at 22 seconds is a result of theaverage time to peak of a 20 ml test bolus injections being 18 secondsand that the rules described in several embodiments mandate that heavierweight subjects have a scan delay of time to peak plus 6 seconds. Thesum of 18 and 6 is 24 which is 2 seconds longer than the injection,allowing the benefit of the diluted phase to hopefully reduce artifact.Furthermore, previous studies have produced favorable aortic enhancementof >300 HU for a fixed injection duration protocol of 25 seconds with anolder generation MSCT scanner. The following rule can be applied forsituations when the computed flow rate exceeds the maximum set by theclinician:

$\begin{matrix}{{R_{C}^{Diag} = {R_{\max}\left\lbrack {{ml}\text{/}s} \right\rbrack}}{{{{{{if}\mspace{14mu}\frac{V_{c}^{Diag}}{R_{C}^{Diag}}} \geq {22\;\sec}}\&}\mspace{14mu}{scanDuration}} \leq {22\mspace{11mu}\sec}}{V_{c}^{Diag} = {R_{C}^{Diag} \cdot 22}}{else}{V_{c}^{Diag} = V_{c}^{Diag}}} & {{Equation}\mspace{14mu} 9}\end{matrix}$

Performing the steps in Equation 9 ensures that the contrast injectionduration is fixed. This operation enforces the condition of a fixedcontrast injection duration for all subjects having scans of n seconds.This is in keeping with results of a number of studies that have shownthat to afford higher aortic enhancement, an increase in the injectionrate must occur. If the clinician chooses to limit the injection flowrate, one can attain a higher plasma concentration if a very longinjection at the limited flow rate (thus a larger volume of contrast) isperformed to allow the recirculation of contrast to accumulate in theblood compartment (also to replace the blood diffusing into theextravascular compartment). This result is not desirable forangiographic applications, however, because of venous contamination andthe asymmetric peak enhancement in the blood vessel compartment ofinterest. Table 2A below sets forth contrast load volumes without flowrate limiting, while Table 2B sets forth contrast load volumes with flowrate limiting (for a maximum flow rate of 5 ml/s) for the case that theinjection duration is clamped at 22 seconds.

TABLE 2A

TABLE 2B

2.3.2 Computation of Dual Flow Contrast and Saline Volume

Dual flow or admixture flow is an optional part of the diagnosticprotocol. The goal for certain cardiac procedures is to fully opacifythe ascending aorta and the coronary arteries while partially opacifyingthe right heart. This is a difficult timing situation where one wantsthe contrast bolus to be in the coronaries while the ratio bolus is inthe right heart. Therefore, one needs to determine the time to switchfrom full contrast to a ratio of contrast and saline. Hereinafter, allparameters with the designation “^” are new parameters after the dualflow adjustment has been made.

The total injection rate for the dual flow phase is the same as thefirst phase rate as indicated in Equation 7. The dual flow contrastvolume is set at the time of protocol generation and is based on theweight of the patient. The following relation provides the dual flowcontrast load volume:V _(C) ^(DF)=0.20[ml/kg]*weight[kg]  Equation 10

The 0.20 coefficient in Equation 10 was computed by analysis ofcollected clinical trial data. A hypothesis of the experiment was toadjust the dual flow duration and dilution ratio based on the time topeak and peak enhancement of a 20 ml timing bolus. The nomogram setforth in Table 3 below is based on the results of that trial. To computethe a priori contrast volume to load before the procedure, a linearregression was performed on the right heart enhancement values from aclinical trial as the dependent variable and the contrast volume as theindependent variable.

A schematic of the timing situation for CTA is depicted in FIG. 28. Thecurves are predicted enhancement curves for the right heart and leftheart compartments as determined by pharmacokinetic simulation. The goalof several studies was to place a hard constraint on the end of fluidinjection at Tend—the sum of scan delay plus scan duration. The deliveryof contrast past the end of the scan duration makes no sense medicallybecause the drug will not contribute to image enhancement. The dilutionphase was computed, per patient, to squeeze in between the end of theinjection duration and Tend. In the studies, the contrast only injectionduration was set to the length of the scan. The “diagnostic”, contrastonly phase duration described will be longer than the scan duration.Because the outcome of the study using the personalized dilutionstrategy produced satisfactory right heart images (defined at rightventricle) and left heart images, the dilution phase contrast volumeswere used as a standard group for this research.

FIG. 29 presents the raw data from a clinical trial for 20 patients. They-axis is the actual volume of contrast used in the dilution phase withthe x-axis the weight of the patients in the sample (in lbs). FIG. 30depicts a Monte-Carlo simulation using biometrics for 70 patients thatcomputed diagnostic and dilution contrast protocols using the preloadedvolume as determined with the coefficients in Table 1 and the volumeprotocols computed with Equations 3 and 10. The study was done toappreciate the volume of residual contrast that would be left in thesyringe after the procedure if a loading factor of 0.12 ml/lb were used.It is evident that the residual contrast wastes for the dilution phaseare below 10 ml. The units of the regression are in pounds. Convertingthe regression coefficient to metric, kg, units results in a coefficientof (0.120[ml/lb]*2.204[lb/kg])=0.264 ml/kg. To reduce the overallcontrast dose, and considering that some of the images in the clinicaltrial had brighter than desired right heart enhancement, the loadingcoefficient for the dual flow phase was set at 0.20 ml/kg. The reductionof the loading factor has an added benefit of reducing the total Iodineburden to the patient.

Dual Flow Saline Volume

There are two instances of the DF saline volume to consider: the loadvolume and the adjusted DF saline volume. The DF saline phase loadvolume is the value that is calculated at the time of generation. It canvary from the adjusted DF saline volume if the ratio changes and has twoscenarios as listed in Table 3 below

TABLE 3 DF Ratio Weight Condition (kg) Ratio Rational No Test bolus <=8530% Since we do not know the exact 102-118 50% level of enhancement weare >118 70% changing the ratio based on body weight. Test bolus 30% Inthe test bolus case, we do not know the actual ratio that we will beusing for the DF adjustment, so we load the worst case for the saline,which is the 30% contrast ratio. This may cause some saline waste duringthe Test Bolus adjustment; however, saline waste is acceptable to theuser.

In all cases for Table 2 above, the saline volume is equal to:V _(S) ^(DF) =V _(C) ^(DF)*((1/Ratio)−1)

If the total volume of contrast computed in the above procedures exceedsthe capacity of the syringe on the system, then steps must be taken toreduce the contrast volume.

2.4 Volume Limiting Based On Syringe Capacity

In several studies of the present invention, 200 ml syringes were used.However, syringes of other volumes, including syringes having a volumeless than 200 ml can be used. For syringe-based injector systems,situations (for example, low concentration contrast and heavy patients)must be accommodated in which it is possible that the computed loadvolume exceeds the volume of the syringe. Table 4 sets forth oneembodiment of a rules set established to ensure that the generatedprotocol and the load volume does not exceed the capacity of thesyringe. In several studies with 200 ml syringes, the maximum loadvolume was set to 195 ml.

TABLE 4 Is there flow rate limiting too? Contrast Reduction algorithmNo 1. Reduce the diagnostic contrast volume until the total calculatedcontrast is equal to the contrast syringe capacity Yes 1. Subtract theDualFlow contrast volume from the diagnostic contrast volume. 2. Ifthere is still an over volume, then reduce the DualFlow volume until 5ml. 3. If there is still an over volume, then delete the DualFlowvolume. 4. If there is still an over volume, then reduce the first phasevolume until the syringe capacity is met.

3.0 Protocol Adjustment Operations

A protocol adjustment subroutine of the present invention modifies theloaded protocol as described above based upon a characterization of thecardiovascular system or a characterization of the propagation of apharmaceutical (for example, including a contrast enhancing agent)through the cardiovascular system. Such characterizations can, forexample, be made through the use of one or more patient models (forexample, parametric models or nonparametric models as described inPublished PCT Application No. WO/2006/055813 (PCT International PatentApplication No. PCT/US2005/041913)) and/or through the use of asmall-volume timing, identification or test bolus or injection. Inseveral embodiments, protocol adjustment was based on data obtained in atest injection (for example, the time to peak and peak enhancement).FIG. 31 illustrates a functional description of an embodiment of aprotocol adjustment function that applies changes to the injectionprotocols based on identification of a test bolus enhancement. Thefollowing subsections are elaborations on the correspondingly numberedoperations described in FIG. 31.

3.1 Computation of Dual Flow Ratio and then Volume

Test bolus adjustments are adjustments made to the protocol after theinjection of the test bolus and the user entering time to peak and peakenhancement. Alternatively, the time to peak and peak enhancement can becommunicated to the protocol generation system of the present inventionvia a wired or wireless communication connection between the scanner andthe system. This calculation does not apply to protocols without a testbolus.

TABLE 5 Peak Enhancement HU Ratio >=140 30% 80 to 139 50%  <79 70%

Based on the heuristic set forth in Table 5, the actual volume ofcontrast to deliver in the dilution (dual flow) phase is computed asfollows:{circumflex over (V)} _(C) ^(DF) ={circumflex over (D)} _(Total)^(DF)×ratio  Equation 11

3.2 Computation of Scan Delay Estimate

The estimate of the scan delay is based on the timing of the injection.The following calculation provides an estimate of the scan delay (in s)based on the measure or estimated values

if weight > = 102 kg (after the weight is discretized)           scanDelay = Tpeak+ 6 Else            scanDelay = Tpeak + 4end if scanDuration < 10 sec (regardless of weight)        scanDelay =Tpeak + 6 end

The additional times of, for example, 4 and 6 seconds are appended tothe time to peak to anticipate the transport delay of contrast from themeasurement site into the region of interest. The 6-second addition isfor heavy patients in whom it is expected that the contrast willpropagate more slowly through the vasculature, and who are more likelyto encounter flow rate limit situations in which the contrast isinjected longer than the scan duration. In the situations in which theprotocol is flow rate limited and the patient weighs less than 102 kg(discretized), there is a chance (especially for lower concentratedcontrast agents) that the end of the injection will occur during thetime to peak of the 20 ml test bolus. It is desirable that the scan notbe started during the injection while the undiluted contrast is in theSVC. The additional time delay anticipates this situation. In asituation in which the clinician performs a very short scan, the scanshould be timed to start during the peak of enhancement.

Because the contrast is preloaded based on weight, a 5-second scanshould make use of the contrast enhancement by starting later in theenhancement window of the left heart. The conditional then, for shortscans less than 10 seconds, determines the duration of the diagnosticphase as time to peak plus 6 seconds to allow the diluted contrast timeto propagate from the peripheral vein vasculature into the heartcompartment—an initial purpose of providing a dilution or dual flowphase. Furthermore, the scan preferably starts after the undilutedcontrast protocol has finished and some of the diluted (dual flow)contrast is reaching the SVC. This result can be realized with shortscan durations, because the concern about imaging during the down slopeof enhancement is less critical.

3.3 Determining if There is Sufficient Time for a Dual Flow Phase

The injection timing adjustment made after the test bolus features areprovided, can, for example, attempt to end the contrast injection at theend of the scan. The following equations apply to the injection timingadjustment:Tend=ScanDelay+ScanDuration

The duration of the dual flow phase is determined by calculating the gapbetween the Tend and the end of the full contrast or contrast only phaseusing the following equation:Dgap=ScanDelay+ScanDuration−D _(C) ^(Diag)

Volume can be adjusted, when applicable, as illustrated in FIGS. 32A and32B.

FIG. 33A through 33G illustrates examples of graphical user interfacesfor use with the embodiment of a protocol generation system of thepresent invention as described above corresponding to various points orsteps along the workflow diagram set forth in FIG. 26.

An upper portion of FIG. 33A illustrates the workflow diagram in whichthe step of patient weight input is encircled with circle A. Acorresponding graphical user interface is illustrated in the lowerportion of FIG. 33A. In this embodiment, patient weight is selected froma plurality of weight ranges. An upper portion of FIG. 33B illustratesthe workflow diagram in which a contrast concentration input step isencircled with circle B. A corresponding graphical user interface isillustrated in the lower portion of FIG. 33B. In this embodiment,contrast concentration is selected from a plurality of availablechoices. An upper portion of FIG. 33C illustrates the workflow diagramin which the syringe loading step is encircled with circle C. Acorresponding graphical user interface or screen display is illustratedin the lower portion of FIG. 33C, in which the contrast syringe andsaline syringe load volumes (as calculated via the method describedabove) are set forth for the user/clinician. An upper portion of FIG.33D illustrates the workflow diagram in which a data transfer step inwhich data from a scout scan is transferred to the interface, isencircled with circle D. A corresponding graphical user interface forentering scan duration is illustrated in the lower portion of FIG. 33D.An upper portion of FIG. 33E illustrates the workflow diagram in whichan initial diagnostic protocol computation step (effected as describedabove) is encircled with circle E. The computed initial or preloadprotocol need not be displayed. A corresponding graphical user interfaceis illustrated in the lower portion of FIG. 33E, wherein the user isprompted to have the protocol generation system generate the protocolby, for example, pressing an OK button. An upper portion FIG. 33Fillustrates the workflow diagram in which a data transfer step in whichdata from a test bolus is transferred to the interface is encircled withcircle F. As clear to those skilled in the art, this data (for example,time to peak and peak enhancement) can be transferred via acommunication link between the scanner and the injector withoutclinician involvement or by manual input by a clinician. A correspondinggraphical user interface for manual data entry of the time to peak andpeak enhancement is illustrated in the lower portion of FIG. 33F. Inthis embodiment, a plurality of-ranges peak enhancement is provided forchoice by the clinician. An upper portion FIG. 33G illustrates theworkflow diagram in which the point at which the determination of theadjusted diagnostic protocol has been completed by the interface and thediagnostic injection can be initiated is encircled with circle G. Acorresponding graphical user interface for setting forth the adjusteddiagnostic protocol is illustrated in the lower portion of FIG. 33D. Theclinician can be provided with the opportunity to change protocolparameters.

FIG. 34A illustrates an embodiment of a display of injector and scannertime lines for a 180 pound male patient undergoing an 8-second CardiacCTA scan. FIG. 34B illustrates representative volumetric flow rates andiodine administration rates for a contrast only phase (phase 1) and adual flow or admixture phase as determined by the protocol generationmethod.

In summary, as discussed above, a number of scan procedures such asCardiovascular MSCT angiography are challenging as a result ofdecreasing acquisition periods and the challenges inherent to contrastagent delivery and use. Moreover, in the case of cardiovascular MSCTangiography cardiac structures are moving during the scan. The timing ofscanner acquisition should coincide with the period when the bolus ofcontrast material provides maximum contrast enhancement in keyanatomical structures. The protocol generation systems and methods ofthe present invention calculate or determine patient personalized CTcontrast medium injection protocols.

In several studies of the protocol generation systems and methods of thepresent invention, a multi-objective optimization's goal was set atleast 350 HU peak enhancement in the left heart compartment of thephysiologic PK model and enhancement greater than 300 HU for at leastthe duration of the scan. Personalized scan delays were computed as afunction of individual cardiac function (scan delay=time to peak of testbolus+4 or 6 seconds depending on patient weight and scan duration). Thepatient's cardiac response determined the duration and contrast tosaline ratio of a dilution phase. Finally, the injection of contrastmaterial was prohibited from extending beyond the end of the scan and,in most cases, ends 5-6 seconds prior.

It was expected that left and right heart contrast enhancement would bemore consistent across subjects using the cardiac protocol generationsystem/method of the present invention as compared to typical methods ofestablishing protocol parameters. To evaluate the level and consistencyof enhancement, cardiac CE CT data from a pilot study were analyzed. Twoanatomic regions of interest (the descending aorta and the rightventricle) were identified in each subject's scan (reconstructed at 60%RR interval) via a semi-automatic segmentation algorithm. For every setof axial slices acquired at a single time point, the mean enhancementwithin each of the regions was computed, yielding time enhancementcurves. The influence of a per-patient, contrast injection protocolhaving a dilution phase on right heart enhancement during cardiac CTAwas also studied. Sufficient enhancement for assessment of the rightheart allows for the assessment of right heart pathology. As illustratedin FIG. 35A, the intersubject variability in the right heart as measuredby the Standard Error of the Mean was lowest in the group in which theprotocol generation system/method of the present invention was used(+/−13 HU). Standard Errors in the other groups were: uni-phasic (+/−39HU)), bi-phasic (+/−39 HU), and fixed dilution phase (+/−28 HU). Aone-way ANOVA (P<0.005) demonstrated that a significant differenceexisted in the mean enhancement values among the injection protocolgroups (also checked with Two sample F-tests for variability, P<0.001).Left Heart Enhancement averaged 325 HU +/−80

A study of 20 patients undergoing cardiovascular CTA (Siemens Sensation64) using injection protocols generated using the system/method of thepresent invention (Iopimidol 370) and 19 control subjects with astandard biphasic protocol (Iopimidol 370 contrast volume=scanduration×5 ml/s, followed by a 40 ml saline flush) was made. All valuesof the time enhancement curves were pooled across subjects, and the twogroups were compared via unpaired t-tests. The mean enhancements for theprotocols generated by the present invention and the biphasic protocolswere 357±69 HU and 323±64 HU, respectively (p=10⁻⁸). The right ventriclemean enhancements were 318±85 HU and 212±96 HU (p=10⁻²¹). These results,illustrated in FIGS. 35B and 35C, respectively, show statisticallysignificant differences in enhancement in both regions.

FIG. 36A illustrates scan results obtained using a protocol generated bya protocol generation process of the present invention for a 139 poundfemale subject while FIG. 36B illustrates scan results obtained using aprotocol generated by a protocol generation process of the presentinvention for a 202 pound male subject. Noticeable in these images isthe bright, uniform opacification of the left heart structures (leftatrium, ventricle, and left anterior descending coronary artery origin).In both images there is also sufficient enhancement of the rightventricle, atrium and superior vena cava to provide for differentiationof the intraventricular septum, the margin of the myocardium. There isalso sufficient opacification to provide for functional analysis ofright ventricular function. Furthermore, enough contrast is present inthe right heart to allow for the diagnosis of thrombo-emboli.Furthermore, visualization of the right ventricle papillary muscles, themoderator band and the tricuspid valve is possible via the presence ofhomogenous contrast enhancement. In both images there is a lack ofstreaking artifact often associated with contrast media residing in thesuperior vena cava, right atrium and right ventricle during CT scanacquisition (see the circle in FIG. 36A). The homogeneity of the rightheart enhancement and lack of streaking artifact is a result of theadministration of a personalized, dilution protocol and optimal scantiming (in relation to the propagation of contrast media in vivo)provided by the systems and methods of the present invention.

In another study of the systems and methods of the present invention,injection protocols were integrated with an injector for cardiacdual-source CT (DSCT). In a study group of 40 consecutive patientsundergoing cardiac DSCT, a parameter generation system/method of thepresent invention as described above, which was implemented via softwareresident on a Medrad STELLANT injector, was prospectively evaluated fordetermining individualized contrast (370 mgI/ml) volume and injectionparameters for a triphasic (contrast, contrast/saline and saline phase)injection protocol. The workflow procedure for the 40 patients of thestudy group was similar to that set forth in FIGS. 33A through 33G.

A control group of another 40 consecutive patients were injected using astandard contrast protocol and retrospectively analyzed to compare thelevel and homogeneity of enhancement within the aorta, coronaryarteries, myocardium and ventricles. The standard protocol was atriphasic protocol in which first phase was a contrast only phase, thesecond phase was an admixture or dual flow phase and the third phase wasa saline only phase. The flow rate was set at 6 ml/second for allphases. The dual flow phase (contrast/saline) was characterized bydelivery of 50 ml of fluid including 30% contrast medium and 70% salineat 6 ml/second. The saline phase was characterized by delivery of 40 mlof saline injected at 6 ml/second. Before the triphasic diagnosticprotocol of the control group, a test bolus of 20 ml of contrast mediumat 6 ml/sec followed by injection of 40 ml of saline 6 ml/second wasused to determine the scan delay, which was determined as the time topeak enhancement in the ascending aorta.

The quality of diagnostic display of cardiac anatomic landmarks wasrated for each of the study group and the control group. FIG. 37 setsforth a graphical representation of answers of two blinded readers ofthe question: “For this patient's intended diagnosis, do you believethat the contrast medium delivery protocol was sufficient to visualizeanatomy and diagnose pathology?” Yes and no responses were accumulatedfor each of the control group and the study group and are set forth aspercent yes/diagnostic or no/non-diagnostic. As set forth in FIG. 37,the blinded readers found that the contrast medium delivery protocolgenerated using the parameter generation system of the present inventionwas sufficient to visualize anatomy and diagnose pathology in 100% ofthe study group patients, while the blinded readers found that thecontrast medium delivery protocol generated using the standardmethodology was sufficient to visualize anatomy and diagnose pathologyin only 92% of the control group patients.

FIG. 38 sets forth a graphical representation of ratings by the blindedreaders of the imaging achieved by each of the contrast medium deliveryprotocol generated using the parameter generation system of the presentinvention (study group) and the standard contrast medium deliveryprotocol for left coronary imaging. In FIG. 38, a rating or “1”corresponds to the conclusion that the structure in question was notvisualized, a rating of “2” corresponds to a conclusion that thestructure in question is faintly visualized, a rating of “3” correspondsto a conclusion that the structure in question is faintly visualized butdelineation is limited, a rating of “4” corresponds to a conclusion thatthe structure in question is visualized and complete delineation ispossible, a rating of “5” corresponds to a conclusion that the structurein question is excellently visualized and delineation is excellent. Asillustrated in FIG. 38, a statistically significant advantage isprovided by the methods and systems of the present invention. FIG. 39sets forth a similar analysis for right coronary imaging. Once again, astatistically significant advantage is provided by the methods andsystems of the present invention. Similar results were observed in otheranatomical structures of the heart.

As illustrated in FIGS. 40 and 41, respectively, mean coronaryattenuation ranged from 359.5±17.7 to 450.6±19.9HU, and from 297.3±11.1to 429.8±10.9HU in the study and control groups. In FIGS. 40 and 41, theabbreviation Ao refers the Ascending Aorta, the abbreviation LtMainrefers to the Left Main Coronary artery, the abbreviation LAD refers tothe Left Anterior Descending Coronary Artery, the abbreviation RCArefers to the Right Coronary Artery and the abbreviation LCx refers tothe Circumflex Coronary Artery. The designations Prox (Proximal), Dist(Distal), and Mid refer to the distal, proximal and mid segments of eachcoronary artery as defined by the American Heart Association 15 segmentcoronary model. Mean attenuation in the distal LAD, mid and distal LCx,and the right ventricle were significantly (p<0.05) higher in the studygroup than in the control group. Intra-subject variability of vascularattenuation was significantly (p<0.002) lower in the study group(SD=49±19.5) than in the control group (SD=63.2±22.1). The diagnosticdisplay of right heart structures (papillary muscles, pulmonary valve,ventricular myocardium), left main, LAD and proximal right coronaryarteries were rated significantly (P<0.05) higher in the study groupthan in the control group. The patient-specific contrast protocolgenerated by the systems and methods of the present invention thusprovided higher and more uniform coronary enhancement and improveddiagnostic display of the heart in cardiac DSCT.

In still another study, enhancement in coronary arteries and ventriclesusing two different triphasic injection protocols with fixed parametersand one injection protocol with individually optimized injectionparameters as determined by a parameter generation system/method of thepresent invention.

In that study, 15 patients were included in each group. In group 1, 70ml of contrast medium (Ultravist 370, Schering) were injected with aflow-rate of 5.0 ml/second in a contrast only phase. In group 2, 80 mlof the contrast medium were injected with a flow-rate of 6.0 ml/secondin a contrast only phase. For group 3 injection parameters werecalculated using the parameter generation system of the presentinvention. Enhancement was measured in the proximal, mid and distalright coronary artery or RCA and in cranial and caudal sections of theright and left ventricle. Measurements were compared using theMann-Whitney-U test.

In each of the control groups, group 1 and group 2, a triphasicinjection protocol was used. In group 1, the flow rate throughout eachof the three phases was 5 ml/second. As set forth above, 70 ml ofcontrast was injected in the first, contrast only phase, of group 1. Inthe second, dual flow, phase of group 1, 50 ml of a mixture of contrastmedium and saline was injected. In the third, saline only, phase ofgroup 1, 40 ml of saline was injected. In group 2, the flow ratethroughout each of the three phases was 6 ml/second. As set forth above,80 ml of contrast was injected in the first, contrast only phase, ofgroup 2. In the second, dual flow, phase of group 2, 50 ml of a mixtureof contrast medium and saline was injected. In the third, saline only,phase of group 2, 40 ml of saline was injected. In both of the group 1and group 2 protocols, a test bolus was performed to determinetiming/scan delay.

Data from the study are set forth in FIGS. 42 through 46. Mean scantimes did not differ significantly. The mean contrast volume applied ingroup 3 was 77.8 ml in the contrast only phase. Enhancement in thecoronary arteries is set forth for groups 1 and 3 in FIG. 42 and forgroups 2 and 3 in FIG. 43. As illustrated in FIG. 42, enhancement in theRCA was significantly higher in all segments of the RCA in group 3 ascompared to group 1 (412.1, 412.5 and 4220HU vs. 358.3, 345.4 and321.8HU). As illustrated in FIG. 43, only the enhancement in the distalRCA differed significantly between group 3 and group 2. Enhancement inthe left and right ventricles is set forth for groups 1 and 3 in FIG. 44and for groups 2 and 3 in FIG. 45. In group 3 significantly higherenhancement was observed towards the end of the exam in the caudal leftventricle. Enhancement in the right ventricle did not differsignificantly.

The study showed that the per-patient determined injection protocols ofthe present invention yielded higher enhancement, especially in thedistal segments of the coronary vessels as compared to injectionprotocols using fixed injection parameters.

FIG. 47 illustrates mean contrast enhancement in another study of fivecoronary segments across 32 subjects. The error bars in FIG. 47represent the standard error of the mean. FIG. 47 illustratesachievement of various design goals of the parameter generationalgorithm of the present invention used in the study. For example, adesirable level of contrast enhancement (for example, at least 350 HU)was achieved across the coronary anatomy. Further, the level ofenhancement was generally consistent over the studied regions of thecoronary anatomy and across subjects (as evidenced by the tight standarderror of the mean). FIG. 48 illustrates mean contrast enhancement infour locations of the right and left ventricles. The measurements weremade by manual placement of an ROI in a cranial (cran) and caudal (caud)section of the Right Ventricle (RV) and Left Ventricle (LV),respectively, in 32 subjects. The error bars of FIG. 48 represent plusand minus standard error of the mean. FIG. 48 illustrates the ability ofthe parameter generation systems of the present invention to providedesired, consistent enhancement in the Left Ventricle. Desiredenhancement in the LV is typically greater than 300 HU for cardiac CTA.In CTA of the heart, one does not desire the right side of the heart tobe enhanced as much as the left heart. However, some contrastenhancement is desired. In the studied embodiment, the parametergeneration system achieved adequate right heart enhancement withoutcausing streak artifacts or beam-hardening artifacts associated withsome current cardiac CTA procedure. The right ventricular enhancementillustrated in FIG. 47 demonstrates adequate enhancement consistentacross subjects (as evidenced by the tight standard error of the mean),and an enhancement level of at least 100 HU less than the left heart.

The representative embodiments set forth above are discussed primarilyin the context of CT imaging. However, the devices, systems and methodsof the present invention have wide applicability to the injection ofpharmaceuticals. For example, the systems devices and methods of thepresent invention can be used in connection with the injection ofcontrast media for imaging procedures other than CT (for example, MRI,ultrasound, PET, etc.).

As briefly described above, the flow rate predicted for a phase (or timeinstance of an injection) can be used as an input to a system or modeladapted or operable to predict the amount of pressure generated in thesyringe or other container as a result of the volumetric flow rate, thefluid path characteristics (for example, the inner diameter of thecatheter (gauge)), and the viscosity of the contrast agent. Generally,the viscosity of contrast medium increases geometrically with respect tothe iodine concentration of the contrast medium in the case of a CTcontrast. The viscosity can be calculated or retrieved from, forexample, a data table. The pressure resulting from a set of values ofthese variables may be computed from fluid dynamics principles as knownin the art or determined from prior experimental data. A discussion ofpressure modeling is set forth in PCT International Patent ApplicationNo. PCT/US05/42891, which sets forth several embodiments of a model orsystem for predicting pressure at various points in an injection fluidpath. If the predicted pressure exceeds a pressure limit or thresholdset by the operator and/or a safe pressure limit determined by themanufacturer of the power injector, the operator can be warned of apossible over-pressure indication by, for example, a color coding of theflow rate entry field. Various other visual, audible and/or tactileindications of a predicted over-pressure situation can be provided.

In general, the embodiments of a parameter generation system describedabove determine the parameters of an initial protocol using informationavailable prior to characterization of the cardiovascular system andpropagation of a pharmaceutical therethrough. The initial protocolprovides information on the volume of one or more fluids to be deliveredto, for example, enable preloading of one or more syringes. Uponcompletion of characterization of the cardiovascular system, theparameters of the protocol are adjusted on the basis of thecharacterization. The parameter generation systems of the presentinvention were described in connection with an injection including aninitial contrast only injection phase and a subsequent admixture phase.As clear to one skilled in the art, the parameter generation system ofthe present invention is applicable to the injection of variouspharmaceuticals, with or without injection of diluent of flushingfluids, via injection protocols that can include one, two of morephases.

Although the present invention has been described in detail inconnection with the above embodiments and/or examples, it should beunderstood that such detail is illustrative and not restrictive, andthat those skilled in the art can make variations without departing fromthe invention. The scope of the invention is indicated by the followingclaims rather than by the foregoing description. All changes andvariations that come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed is:
 1. A system, comprising: a first pressurizing drivemember adapted to be operably associated with at least a first fluidcontainer, the first fluid container being adapted to contain apharmaceutical comprising a contrast enhancing agent to be injected inan imaging procedure; and a controller operably associated with thefirst pressurizing drive member, the controller comprising a programmingsystem to allow programming of an injection protocol via which injectionof the pharmaceutical from the at least a first fluid container iscontrolled, the injection protocol comprising at least a first phase; aparameter generation system in communication with the controller andcomprising a processor, a memory system and an input system, theprocessor executing an algorithm stored in the memory system, thealgorithm determining parameters of the at least a first phase of theinjection protocol based at least in part upon a type of the injectionprotocol identified via the input system, wherein the parametergeneration system determines a volume of the pharmaceutical that is tobe delivered to a patient at least partly on the basis of aconcentration of the contrast enhancing agent in the pharmaceuticalidentified via the input system and at least partly on the basis of afunction X having a value that differs depending upon a weight of thepatient input via the input system.
 2. The system of claim 1 wherein atleast a first portion V₁ of the volume of the pharmaceutical to bedelivered to the patient is calculated using the formula:V ₁=weight*X*Y, wherein Y is a function of the concentration of thecontrast enhancing agent in the pharmaceutical.
 3. The system of claim 2wherein X is determined for the weight of a particular patient from analgorithm in which X is calculated as a function of weight.
 4. Thesystem of claim 2 wherein X is determined for the weight of a particularpatient from a table wherein X is set forth as a function of weight. 5.The system of claim 2 further comprising: a second pressurizing drivemember adapted to be operably associated with at least a second fluidcontainer, the second fluid container adapted to contain a diluentfluid; wherein the controller is operably associated with the secondpressurizing drive member, and wherein V₁ is the volume of thepharmaceutical to be delivered in a phase in which only thepharmaceutical is to be delivered to the patient, the parametergeneration system also determining a volume V₂ of the pharmaceutical tobe delivered in at least a second phase in which both the pharmaceuticaland the diluent fluid are to be delivered to the patient.
 6. The systemof claim 5 wherein a flow rate of the pharmaceutical delivered in thefirst phase is approximately equal to a flow rate of an admixture of thepharmaceutical and the diluent fluid delivered in the second phase. 7.The system of claim 6 wherein the flow rate of the pharmaceutical iscalculated by dividing V₁ by an injection duration of the first phase.8. The system of claim 7 wherein the injection duration of the firstphase is determined by adding a factor K to a scan duration of animaging system.
 9. The system of claim 8 wherein K ranges from 0 to 10seconds.
 10. The system of claim 9 wherein a minimum for the injectionduration of the first phase can be input into the parameter generationsystem.
 11. The system of claim 10 wherein the flow rate of thepharmaceutical delivered in the first phase is calculated by dividing V₁by the injection duration of the first phase.
 12. The system of claim 6wherein the volume V₂ of the pharmaceutical to be delivered to thepatient in the second phase is calculated based at least in part on aparameter of the patient selected from the group consisting of weight,body mass index, body surface area, and cardiac output.
 13. The systemof claim 12 wherein the parameter generation system determines whether atotal volume of the pharmaceutical to be delivered to the patient in allphases exceeds an available volume of the pharmaceutical available fordelivery to the patient, the parameter generation system furthercomprising rules to reduce the total volume of the pharmaceutical if thetotal volume exceeds the available volume.
 14. The system of claim 5wherein a total volume of the pharmaceutical to be delivered to thepatient in all phases is determined.
 15. The system of claim 14 whereinan initial protocol determined by the parameter generation system todetermine the total volume of the pharmaceutical to be delivered to thepatient is adjusted based upon a characterization of a cardiovascularsystem of the patient.
 16. The system of claim 15 wherein a test bolusof the pharmaceutical is performed to characterize the cardiovascularsystem of the patient.
 17. The system of claim 16 wherein the initialprotocol is adjusted at least in part on the basis of a time to peakenhancement of the test bolus.
 18. The system of claim 16 wherein theinitial protocol is adjusted at least in part on the basis of a time topeak enhancement of the test bolus and a level of enhancement of thepeak enhancement.
 19. The system of claim 2 wherein X decreasesnonlinearly with increasing weight of the patient.